OVERVIEW
A channel is a representation of sound coming from or going to a single point. A single microphone can produce one channel of audio, and a single speaker can accept one channel of audio, for example.
A digital audio file can contain multiple channels of data. Music that is mixed for headphone listening is saved as a file with two channels - one sent to the left ear, one sent to the right, while surround-sound movie audio is often mixed for 6 channels.