The Selection Panes are the places in Ultra Recall that drive what content is displayed throughout the application. Only one of these Selection Panes can be active at one time, and the active Pane will have its selection visible (highlighted).
The Selection Panes include:
|•||Web Toolbar †|
† this isn't technically a Pane, but when it is displaying a URL, it functions as a Selection Pane (it is active whenever it contains a URL)