Apple's accordion module provides a method for displaying a good deal of informational and promotional content without overwhelming the interface. The types of things that are displayed in these are accordions are usually supporting content, so the desire to use a design pattern that hides and shows these panels of content is useful. Only one panel is visible at a time, and hovering over or clicking a panel heading brings its content into view with a smooth slide transition.

1. Supporting information, news, and store locations is displayed in an accordion of panels at the right.
2. Hovering over one of the blue panel headings displays that panel and hides all others.
3. On the "Downloads" page, download categories and top 10 lists of downloads are displayed.
4. The "Top Apple Downloads" panel in view.

http://www.apple.com/mac/