00 Stereo Similar to Dual mono, 2 channels, but bitrate can be different for each one and is coded dynamically. Eg. if channel 1 is silent, the second one will get higher bitrate.
01 Joint Stereo Mostly used in MP3. One channel is common (mid) and is used mainly for common and lower tones. The second is (side) channel for encoding differences between normal channels.
Note: Stereo effect is listenable properly only for higher tones because for lower ones is length of sound wave so long that you are not able to distinguish phase move.
10 Dual Also known as Dual mono; 2 separate channels.
11 Mono (single channel Normal mono.