Minor typo changes.

admin_toolbar.info.yml

 name: Admin Toolbar
 core: 8.x
-description: Admin Toolbar improve the default Drupal Toolbar,it lets the hover of sub menus.
+description: Admin Toolbar improves the core Drupal Toolbar by providing a drop-down menu interface.
 package: Administration
 type: module
 dependencies:

admin_toolbar.module

 <?php
+
+/**
+ * @file
+ * This is the module to create a drop-down menu for the core toolbar.
+ */
+
 use Drupal\Core\Menu\MenuTreeParameters;
+
 /**
  *  Implements hook_toolbar_alter().
  */

admin_toolbar_tools/admin_toolbar_tools.module

 <?php
 
-use Drupal\Core\Routing\RouteMatchInterface;
-
 /**
  * @file
- * Prvides extra menu links for admin_toolbar.
+ * Provides extra menu links for the core drupal toolbar.
  */
 
+use Drupal\Core\Routing\RouteMatchInterface;
+
 /**
  * Implements hook_toolbar().
  */