the bit rate is a measure of how miny 'bits' of data have been copied (ripped) in converting the file from its original 'wav' format (on the CD) to the mp3 format on the pc - the more bits (ie the higher the bit rate) the closer the mp3 will sound to the original CD

a bit rate of 128 kb/sec is sort of the most common but mp3 files sound much better if the bit rate is higher (usually - 160 or 192 or 256 or 320)

the only drawback is the higher the bit rate the bigger the file - but if you've got the space and don't mind the longer download time - the higher bit rate files sound much much better than low bit rate files

cheers, bad_vlad