docs/guide/usage-widgets.md revised for readability [ci skip]

docs/guide/usage-widgets.md

@@ -19,15 +19,14 @@ framework features. All widgets belong to `\yii\bootstrap` namespace:
 - [[yii\bootstrap\Tabs|Tabs]]
 
 
-## Customize widget CSS classes <span id="widgets-customize-css-classes"></span>
+## Customizing widget CSS classes <span id="customizing-css-classes"></span>
 
-Widgets allow quick composition of the HTML for particular Bootstrap components, which requires usage of the
+These widgets allow quick composition of the HTML for the Bootstrap components that require the use of the Bootstrap CSS classes.
-Bootstrap CSS classes. Those classes are added automatically by the widgets. However usually widget provides
+The default class for the component is added automatically by the widget, and the optional classes that you may want to customize are usually supported through the properties of the widget.
-fields or properties, which allow customization of the CSS styles for particular HTML tags.
 
-For example: you may use [[yii\bootstrap\Button::options]] to customize appearance of the rendered button.
+For example, you may use [[yii\bootstrap\Button::options]] to customize the appearance of a button.
-Class 'btn' will be added automatically, so you don't need to worry about it. All you need is specify particular
+The class 'btn' which is required for a button will be added automatically, so you don't need to worry about it.
-button class:
+All you need is specify a particular button class:
 
 ```php
 echo Button::widget([
@@ -36,17 +35,16 @@ echo Button::widget([
 ]);
 ```
 
-However, sometimes you may need to replace standard class, added by the widget, with alternative one.
+However, sometimes you may need to replace the default class with an alternative one.
-For example: widget [[yii\bootstrap\ButtonGroup]] uses 'btn-group' class for the container div, but you may
+For example, the widget [[yii\bootstrap\ButtonGroup]] uses 'btn-group' class for the container div by default,
-need to use 'btn-group-vertical', which allows vertical-style layout for the buttons. Using plain 'class' option
+but you may need to use 'btn-group-vertical' instead to align the buttons vertically.
-simply adds 'btn-group-vertical' to 'btn-group', which produces incorrect result.
+Using a plain 'class' option simply adds 'btn-group-vertical' to 'btn-group', which will produce an incorrect result.
-In order to actually replace class added by widget, you need to specify 'class' option as array, containing
+In order to override the default class of a widget, you need to specify the 'class' option as an array that contains the customized class name under the 'widget' key:
-needed class name under the 'widget' key:
 
 ```php
 echo ButtonGroup::widget([
     'options' => [
-        'class' => ['widget' => 'btn-group-vertical'] // replace 'btn-group' with 'btn-group-vertical'
+        'class' => ['widget' => 'btn-group-vertical'] // replaces 'btn-group' with 'btn-group-vertical'
     ],
     'buttons' => [
         ['label' => 'A'],