It's an online music site where you can play the whole tune of a very big library of tunes. NOT like iTunes where you can only play 30 seconds of a track. It's an application which you have to download - no big deal . . .
The Downside is that you have to listen to madverts every so often.
Also there is no Beatles, Led Zep or Floyd for you old hippies. The Stones are all there . . . and Bowie . . .
Give it a go.