a. A high level menu of items that are always available for the user.
b. A second level list of items that the high level menu items point to
c. A detailed information page that each second level item reveals.
An Example iPad application
Let's take the example of Twitter for iPad, a widely used and popular application. In the twitter application, the timeline, @mentions, messages, lists, profile and search are the items that are always available. These are level 1 items in the twitter app. The list of tweets are the second level elements. A detailed page revealed by a tweet is the level 3 screen element. An example of Level 1 and Level 2 screen elements
An example of level 3 screen elements When an item in level 2 is tapped a detailed page is normally displayed. We shall refer to this detailed page as level 3 for the sake of our prototype. You will notice that there are several icons on level 3 using which the user can perform various actions. These actions are normally for creating, sharing or organizing information.
On each details page, a person will be able to consume information and perform certain actions.