It's an attractive, compact little program, with a graphic interface that lets you play all your mp3 files as well as standard Windows audio files and CD's. There are dozens of options within the player, but the main ones are the graphic equalizer and playlist. The graphic equalizer is virtually the same as the one on your home stereo, letting you control different levels of your audio, and improve whatever parts of it you like. The playlist lets you create and then save your own collections of music. The other popular element for WinAmp users is the trading of player skins.
Skins are the visual look that the program takes - and they're completely customisable.
The Nullsoft site alone has over 3000 skins to choose from, everything from an X-Files to a Pepsi look. The WinAmp site is easily the best place to start as it gives you a download link to the fast Australian mirror site, the thousands of skins I mentioned, and plenty of tips on how to use the program. It's a completely free program, which makes it even better to use.