What is Audio Bitrate?
TL;DR: Audio bitrate is the amount of data used per second of audio, measured in kbps (kilobits per second). Higher bitrate means more detail preserved, better sound quality, and larger files.
Common bitrates: 128 kbps (good for speech/podcasts), 192 kbps (good quality music), 256 kbps (high quality), 320 kbps (maximum MP3 quality, nearly indistinguishable from CD). For reference, CD audio is 1,411 kbps uncompressed.