Groups and submixes are related to each other and often get confusing, but there is one simple difference. Submixes are when multiple tracks are sent through a separate bus or path hat eventually (usually) makes it back to the master out. Groups are simply linking multiple track’s faders (among other functions) so that if you move one, they all move together. A group is handy to let you adjust multiple faders at once, mute or solo a handful of tracks, or apply automation to a bunch of tracks at once. A VCA is a type of track that can be used to control a group. It can be very handy, because by adjusting the VCA fader, you will adjust all of the faders of the group. But if you want to adjust the volume of a single fader, you can move that individual fader without affecting the entire group.