This is used to describe the capabilities of the software or hardware you are using. Basically when recording a song different instruments are placed on different channels. Most people equate tracks with channels but technically they are different. MIDI devices generally have 16 channels, meaning 16 different instruments can be sounded at one time. eg A piano might be recorded on channel 1, a bass guitar on channel 2, a saxophone on channel 3 etc. People who want a full orchestra may require up to 64 channels, because they want up to 64 separate instruments to play at once. Also see tracks.