What is the difference between Alpha Matte and Luma Matte in After Effects?

I often got Alpha and Luma matte confused when I was getting started in After Effects. I would cycle through them until I achieved the look I was going for. You shouldn't have to do that!
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[@1WillyDAVID]

Great explanation man, thanks a lot!

[@BallerFX]

Thanks William, glad you found it helpful!

[@Infinitends]

gg great exp. cheers

[@BallerFX]

Glad you found it helpful!