Did you use the search button to try & find your answers? Go here http://en.wikipedia.org/wiki/Gnutella & type in the search box the things you want to know.

As far as burning cd's, aiff & wav are rarely shared. And other compressed but lossless formats such as apple lossless (m4a files more than 320 kbps), or ape or flac also not common. To find out about burning cd's see Burning an audio CD from your MP3's