Basically, you enter a song (or an artist) and it creates a music station tailored to you. You can add more songs and also rate each song that plays to further customize. I like it because it plays stuff that I haven't heard too much of and am, therefore, tired of. You can create multiple stations for your multiple personalities (I guess that should be... multiple moods).
BTW, David Bowie makes a good first choice (thanks to my 8 year old daughter for suggesting him. What can I say? She's got pretty good taste in music).