The organization tree allows you to quickly navigate throughout your library. Your library consists of imported media files, an assortment of Playlists and Smartlists, links to stores and services and the contents of various devices (CD-ROM, CD-RW, Handhelds, Remotes).
You can use keyboard hot-keys (or accelerators) to navigate around the organization tree without the use of the mouse.
You can also access the organization tree by going to File > Quick Play. This way you still have access to the organization tree items even when the organization tree is hidden (by double clicking the vertical splitter bar).
The selection that is displayed in between Playing Now and Playlists will vary, depending on which Media Mode has been selected (under the search bar, top right). This feature permits you to view only images related library information, for example, when the Images Media Mode is selected.
To Hide/View the Organization Tree
In between the organization tree and the content pane to its right there is a vertical splitter bar. Hover over it, and drag it left or right.