Help with itunes?

I just got an ipod shuffle. and im soo psyched since i always used my bulky mp3 player. And, i usually download my songs from limewire. But what is the purpose of itunes if i dont get my songs from them? is it just for organizing your songs into a library or something? help me? and if i do need itunes, plsz give me a link to download for free, and i just want the library managing thing, thank yo uso much. all answers will be considered as lifesavers. and the best one will be chosen.