bit rate 
In data communications, the bit rate is the measure of how many bits of data are transmitted or received (say, from a modem) in a specified amount of time, such as kilobits per second. In digital audio, it's a measure of how many bits describe each sound in an audio file. Generally speaking, a low bit rate means lower sound quality and a smaller file size, while a high bit rate means better quality and larger files. However, compression algorithms vary. For instance, a 96Kbps (kilobits per second) MP3 Pro file may sound better than a 160Kbps MP3 file, or a 1Mbps (megabits per second) DivX file may look better than a 2Mbps MPEG-1 file.