Sounds can have different numbers of channels, and those channels can map to various speaker layouts.

mono1 channel.
stereo2 channels. The first channel is for the left speaker and the second is for the right.
ambisonic4 channels. Ambisonic channels don't map directly to speakers but instead represent directions in 3D space, sort of like the images of a skybox. Currently, ambisonic sounds can only be loaded, not played.

See also