In a nut shell, rockbox replaces the stock ipod firmware to play music in almost any format (mp3, flac, etc) and toss out the annoying iTune. It renders the ipod basically a portable hard drive so you can drag and drop to load your music files and/or non-music files. There are more with the rockbox (e.g. EQ's).
It's my understanding there is no officially stable version of RB for the ipod classic's.
ok thanks. i dont use the eq settings on my ipod anyway, if i want to use it, ill use it on my amp but i usually dont even touch that, just setting it on flat. and about the formats, that will be nice because i always have to convert my flac files to apple lossless. and how about higher bitrates and higher sampling rates? i have like 5 songs that are in 24 bit 96 kHz and my ipod wont support that, will rockbox make my ipod capable of holding these 5 songs?