Click tracks are just like a metronome. Simply put, it’s just a click that is set at a specific tempo. Usually the click is in the ear of the drummer and some or all of the musicians in a band, and it keeps everyone on time.
To use click tracks, you’ll need at least someone using in-ear monitors, as you wouldn’t want the click to be heard by everyone in the room – only the musicians.
A loop is a 4-8 bar phrase (could be more or less) that just repeats in time. Usually loops are a percussion or drum beat of some kind. It simply repeats while the band plays over the top, and can be started and stopped at any time.
You don’t necessarily need in ear monitors for a loop – you just have to be able to play in time to it.
Multitracks include a click track and typically a cue track, but they also include other instrumentation. Full multitracks include every instrument that is in the studio recording of a song. Usually you get the individual instruments as audio files and you can choose which instruments you want to include and how they are mixed. They are meant to supplement a band live.
(this is our multitrack for Wake by Hillsong Young and Free, and all instruments are mixed with the click and cue track)