A VCA is a useful tool. In Logic Pro X you can create a VCA with a “Folder Stack”.
A VCA Channel has a fader, but it doesn’t pass audio. Instead, the fader acts like a gain control for other channels, or groups of channels. In some ways, you can think of a VCA Channel as “remote control” for other channels. If you assign a VCA to control a channel, you can adjust the channel gain, without having to move the associated channel’s fader. The VCA Channel fader does it for you.