First round of edits

docs/guide/validation.md

 Model validation reference
 ==========================
 
-This guide section doesn't describe how validation works but instead describes all Yii validators and their parameters.
-In order to learn model validation basics please refer to [Model, Validation subsection](model.md#Validation).
+As a model both represents data and defines the business rules to which that data must adhere, comprehending data validation is key to using Yii. In order to learn model validation basics, please refer to [Model, Validation subsection](model.md#Validation).
+
+This guide describes all of Yii's validators and their parameters.
+
 
 Standard Yii validators
 -----------------------
 
-Standard Yii validators could be specified using aliases instead of referring to class names. Here's the list of all
-validators bundled with Yii with their most useful properties:
+The standard Yii validators are defined in many Yii classes, found primarily within the `yii\validators` namespace. But you do not need to specify the full namespace for the standard Yii validators as Yii can recognize them from defined aliases. 
+
+Here's the list of all validators bundled with the Yii framework, including  their most useful properties. The default value for each property is indicated in parentheses. Note that this does not present an exhaustive list of each validator's properties.  
 
 ### `boolean`: [[yii\validators\BooleanValidator|BooleanValidator]]
 
@@ -16,77 +19,77 @@ Checks if the attribute value is a boolean value.
 
 - `trueValue`, the value representing true status. _(1)_
 - `falseValue`, the value representing false status. _(0)_
-- `strict`, whether to compare the type of the value and `trueValue`/`falseValue`. _(false)_
+- `strict`, whether to also compare the type of the value and `trueValue`/`falseValue`. _(false)_
 
 ### `captcha`: [[yii\captcha\CaptchaValidator|CaptchaValidator]]
 
 Validates that the attribute value is the same as the verification code displayed in the CAPTCHA. Should be used together
 with [[yii\captcha\CaptchaAction]].
 
-- `caseSensitive` whether the comparison is case sensitive. _(false)_
-- `captchaAction` the route of the controller action that renders the CAPTCHA image. _('site/captcha')_
+- `caseSensitive`, whether the comparison is case sensitive. _(false)_
+- `captchaAction`, the route of the controller action that renders the CAPTCHA image. _('site/captcha')_
 
 ### `compare`: [[yii\validators\CompareValidator|CompareValidator]]
 
 Compares the specified attribute value with another value and validates if they are equal.
 
-- `compareAttribute` the name of the attribute to be compared with. _(currentAttribute_repeat)_
-- `compareValue` the constant value to be compared with.
-- `operator` the operator for comparison. _('==')_
+- `compareAttribute`, the name of the attribute to be compared with. _(currentAttributeName_repeat)_
+- `compareValue`, a constant value to be compared with.
+- `operator`, the operator for the comparison. _('==')_
 
 ### `date`: [[yii\validators\DateValidator|DateValidator]]
 
-Verifies if the attribute represents a date, time or datetime in a proper format.
+Verifies if the attribute represents a date, time, or datetime in a proper format.
 
-- `format` the date format that the value being validated should follow according to
+- `format`, the date format that the value being validated should follow according to
   [PHP date_create_from_format](http://www.php.net/manual/en/datetime.createfromformat.php). _('Y-m-d')_
-- `timestampAttribute` the name of the attribute to receive the parsing result.
+- `timestampAttribute`, the name of the attribute that should receive the parsed result.
 
 ### `default`: [[yii\validators\DefaultValueValidator|DefaultValueValidator]]
 
 Sets the attribute to be the specified default value.
 
-- `value` the default value to be set to the specified attributes.
+- `value`, the default value to be assigned.
 
 ### `double`: [[yii\validators\NumberValidator|NumberValidator]]
 
-Validates that the attribute value is a number.
+Validates that the attribute value is a number, integer or decimal.
 
-- `max` limit of the number. _(null)_
-- `min` lower limit of the number. _(null)_
+- `max`, the upper limit of the number (inclusive). _(null)_
+- `min`, the lower limit of the number (inclusive). _(null)_
 
 ### `email`: [[yii\validators\EmailValidator|EmailValidator]]
 
-Validates that the attribute value is a valid email address.
+Validates that the attribute value is a valid email address. By default, this validator checks if the attribute value is a syntactical valid email address, but the validator can be configured to check the address's domain for the address's existence.
 
-- `allowName` whether to allow name in the email address (e.g. `John Smith <john.smith@example.com>`). _(false)_.
-- `checkMX` whether to check the MX record for the email address. _(false)_
-- `checkPort` whether to check port 25 for the email address. _(false)_
-- `enableIDN` whether validation process should take into account IDN (internationalized domain names). _(false)_
+- `allowName`, whether to allow the name in the email address (e.g. `John Smith <john.smith@example.com>`). _(false)_.
+- `checkMX`, whether to check the MX record for the email address. _(false)_
+- `checkPort`, whether to check port 25 for the email address. _(false)_
+- `enableIDN`, whether the validation process should take into account IDN (internationalized domain names). _(false)_
 
 ### `exist`: [[yii\validators\ExistValidator|ExistValidator]]
 
 Validates that the attribute value exists in a table.
 
-- `targetClass` the ActiveRecord class name or alias of the class that should be used to look for the attribute value being
+- `targetClass`, the ActiveRecord class name or alias of the class that should be used to look for the attribute value being
   validated. _(ActiveRecord class of the attribute being validated)_
-- `targetAttribute` the ActiveRecord attribute name that should be used to look for the attribute value being validated.
+- `targetAttribute`, the ActiveRecord attribute name that should be used to look for the attribute value being validated.
   _(name of the attribute being validated)_
 
 ### `file`: [[yii\validators\FileValidator|FileValidator]]
 
 Verifies if an attribute is receiving a valid uploaded file.
 
-- `types` a list of file name extensions that are allowed to be uploaded. _(any)_
-- `minSize` the minimum number of bytes required for the uploaded file.
-- `maxSize` the maximum number of bytes required for the uploaded file.
-- `maxFiles` the maximum file count the given attribute can hold. _(1)_
+- `types`, an array of file name extensions that are allowed to be uploaded. _(any)_
+- `minSize`, the minimum number of bytes required for the uploaded file.
+- `maxSize`, the maximum number of bytes allowed for the uploaded file.
+- `maxFiles`, the maximum number of files that the given attribute can hold. _(1)_
 
 ### `filter`: [[yii\validators\FilterValidator|FilterValidator]]
 
-Converts the attribute value according to a filter.
+Converts the attribute value by sending it through a filter.
 
-- `filter` PHP callback that defines a filter.
+- `filter`, a PHP callback that defines a filter.
 
 Typically a callback is either the name of PHP function:
 
@@ -107,19 +110,20 @@ Or an anonymous function:
 
 Validates that the attribute value is among a list of values.
 
-- `range` list of valid values that the attribute value should be among.
-- `strict` whether the comparison is strict (both type and value must be the same). _(false)_
-- `not` whether to invert the validation logic. _(false)_
+- `range`, a list of valid values that the attribute value should be among (inclusive).
+- `strict`, whether the comparison should be strict (both the type and value must be the same). _(false)_
+- `not`, whether to invert the validation logic. _(false)_
 
 ### `inline`: [[yii\validators\InlineValidator|InlineValidator]]
 
 Uses a custom function to validate the attribute. You need to define a public method in your
-model class which will evaluate the validity of the attribute. For example, if an attribute
-needs to be divisible by 10. In the rules you would define: `['attributeName', 'myValidationMethod'],`.
+model class that will evaluate the validity of the attribute. For example, if an attribute
+needs to be divisible by 10, in the rules you would define: `['attributeName', 'isDivisibleByTen']`.
 
 Then, your own method could look like this:
+
 ```php
-public function myValidationMethod($attribute) {
+public function isDivisibleByTen($attribute) {
     if (($this->$attribute % 10) != 0) {
          $this->addError($attribute, 'cannot divide value by 10');
     }
@@ -128,32 +132,32 @@ public function myValidationMethod($attribute) {
 
 ### `integer`: [[yii\validators\NumberValidator|NumberValidator]]
 
-Validates that the attribute value is an integer number.
+Validates that the attribute value is an integer.
 
-- `max` limit of the number. _(null)_
-- `min` lower limit of the number. _(null)_
+- `max`, the upper limit of the number (inclusive). _(null)_
+- `min`, the lower limit of the number (inclusive). _(null)_
 
 ### `match`: [[yii\validators\RegularExpressionValidator|RegularExpressionValidator]]
 
-Validates that the attribute value matches the specified pattern defined by regular expression.
+Validates that the attribute value matches the specified pattern defined by a regular expression.
 
-- `pattern` the regular expression to be matched with.
-- `not` whether to invert the validation logic. _(false)_
+- `pattern`, the regular expression to be matched.
+- `not`, whether to invert the validation logic. _(false)_
 
 ### `number`: [[yii\validators\NumberValidator|NumberValidator]]
 
 Validates that the attribute value is a number.
 
-- `max` limit of the number. _(null)_
-- `min` lower limit of the number. _(null)_
+- `max`, the upper limit of the number (inclusive). _(null)_
+- `min`, the lower limit of the number (inclusive). _(null)_
 
 ### `required`: [[yii\validators\RequiredValidator|RequiredValidator]]
 
-Validates that the specified attribute does not have null or empty value.
+Validates that the specified attribute does not have a null or empty value.
 
-- `requiredValue` the desired value that the attribute must have. _(any)_
-- `strict` whether the comparison between the attribute value and
-  [[yii\validators\RequiredValidator::requiredValue|requiredValue]] is strict. _(false)_
+- `requiredValue`, the desired value that the attribute must have. _(any)_
+- `strict`, whether the comparison between the attribute value and
+  [[yii\validators\RequiredValidator::requiredValue|requiredValue]] must match both value and type. _(false)_
 
 ### `safe`: [[yii\validators\SafeValidator|SafeValidator]]
 
@@ -163,35 +167,34 @@ Serves as a dummy validator whose main purpose is to mark the attributes to be s
 
 Validates that the attribute value is of certain length.
 
-- `length` specifies the length limit of the value to be validated. Can be `exactly X`, `[min X]`, `[min X, max Y]`.
-- `max`  maximum length. If not set, it means no maximum length limit.
-- `min` minimum length. If not set, it means no minimum length limit.
-- `encoding` the encoding of the string value to be validated. _([[yii\base\Application::charset]])_
+- `length`, specifies the length limit of the value to be validated (inclusive). Can be `exactly X`, `[min X]`, `[min X, max Y]`.
+- `max`, the upper length limit (inclusive). If not set, it means no maximum length limit.
+- `min`, the lower length limit (inclusive). If not set, it means no minimum length limit.
+- `encoding`, the encoding of the string value to be validated. _([[yii\base\Application::charset]])_
 
 ### `unique`: [[yii\validators\UniqueValidator|UniqueValidator]]
 
 Validates that the attribute value is unique in the corresponding database table.
 
-- `targetClass` the ActiveRecord class name or alias of the class that should be used to look for the attribute value being
+- `targetClass`, the ActiveRecord class name or alias of the class that should be used to look for the attribute value being
   validated. _(ActiveRecord class of the attribute being validated)_
-- `targetAttribute` the ActiveRecord attribute name that should be used to look for the attribute value being validated.
+- `targetAttribute`, the ActiveRecord attribute name that should be used to look for the attribute value being validated.
   _(name of the attribute being validated)_
 
 ### `url`: [[yii\validators\UrlValidator|UrlValidator]]
 
 Validates that the attribute value is a valid http or https URL.
 
-- `validSchemes` list of URI schemes which should be considered valid. _['http', 'https']_
-- `defaultScheme` the default URI scheme. If the input doesn't contain the scheme part, the default scheme will be
+- `validSchemes`, an array of URI schemes that should be considered valid. _['http', 'https']_
+- `defaultScheme`, the default URI scheme. If the input doesn't contain the scheme part, the default scheme will be
   prepended to it. _(null)_
-- `enableIDN` whether validation process should take into account IDN (internationalized domain names). _(false)_
+- `enableIDN`, whether the validation process should take into account IDN (internationalized domain names). _(false)_
 
 Validating values out of model context
 --------------------------------------
 
-Sometimes you need to validate a value that is not bound to any model such as email. In Yii `Validator` class has
-`validateValue` method that can help you with it. Not all validator classes have it implemented but the ones that can
-operate without model do. In our case to validate an email we can do the following:
+Sometimes you need to validate a value that is not bound to any model, such as a standalone email address. The `Validator` class has a
+`validateValue` method that can help you in these scenarios. Not all validator classes have implemented this method, but the ones that have implemented `validateValue` can be used without a model. For example, to validate an email stored in a string, you can do the following:
 
 ```php
 $email = 'test@example.com';