diff --git a/tutorials/action_system.md b/tutorials/action_system.md
index 0f083fc30..c013fc3cc 100644
--- a/tutorials/action_system.md
+++ b/tutorials/action_system.md
@@ -1,2 +1,9 @@
 IntelliJ Action System
 ==========
+The system of actions allows plugins to add their own items to IDEA menus and toolbars.
+An action is a class, derived from the [AnAction] (https://github.com/JetBrains/intellij-community/blob/master/platform/editor-ui-api/src/com/intellij/openapi/actionSystem/AnAction.java) class,
+whose actionPerformed method is called when the menu item or toolbar button is selected.
+For example, one of the action classes is responsible for the "File | Open File..." menu item and for the "Open File" toolbar button.
+Actions may be organized into groups, which, in turn, can contain other groups. A group of actions can form a toolbar or a menu.
+Subgroups of the group can form submenus of the menu.
+