For the uninitiated, 640 kbps (kilobits per second) refers to a bitrate commonly used in audio compression. In the context of MP3 encoding, a 640 kbps file typically uses a relatively high bitrate to balance file size and audio quality. This bitrate is higher than the standard 128-192 kbps often used in the early days of digital music, but lower than the 1,411 kbps (or 1.4 Mbps) required for CD-quality audio.