Every track you play will tell your Last.fm profile something about what you like. It can connect you to other people who like what you like - and recommend songs from their music collections and yours too.
When you recommend some music to a friend, or you tag it, or you write about it - even just listening to it - you shift the song's importance on the site. It'll be recommended to different people, because you've listened to it. It'll move up our music charts and maybe more people will hear it because you thought it was good.
Yep, all you need to do is join the group at the link below, it's instant, and free! See the music you've played up there today!