User interface...wikipedia

iPods with color displays use anti-aliased graphics and text, with sliding animations. All iPods (except the current iPod Shuffle and iPod Touch) have five buttons and the later generations have the buttons integrated into the click wheel—an innovation that gives an uncluttered, minimalist interface. The buttons perform basic functions such as menu, play, pause, next track, and previous track. Other operations, such as scrolling through menu items and controlling the volume, are performed by using the click wheel in a rotational manner. The current iPod Shuffle does not have any controls on the actual player; instead it has a small control on the earphone cable, with volume-up and -down buttons and a single button for play/pause, next track, etc. The iPod Touch has no click-wheel; instead it uses a 3.5" touch screen in addition to a home button, sleep/wake button and (on the second and third generations of the iPod touch) volume-up and -down buttons. The user interface for the iPod touch is virtually identical to that of the iPhone. Both devices use the iPhone OS.