Have you ever heard in the beginning of a gospel concert the sound of cymbals, hi-hat, or some shakers right before the song starts. Have you ever heard drummers practicing to a very minimal drum loop track? Well this is what we call in the industry: Click Tracks.
Click tracks can also be used as a way for drummers to shed and practice. sometimes as drummers you want a way to be able to practice alongside tracks and beats, without all of the instruments. A metronome is boring, so click tracks are a way to liven up the sound.
You can also use click-tracks in productions. The way you do this is lay the track down, then lay all of the other instruments over it. You can always lay drums later, but now you have a way to record your tracks and songs with a little more inspiration by having good sound click tracks behind you.