Very new to GIMP and looking to recreate an effect from a YT video.

[Reptorian]

Some tutorials made for PS can be used in GIMP. I used tutorials on so many other programs other than what it is made for. The effect the OP is looking for is nondestructive layer effects. It lools like layer mask, and it doesn't look like adjustment layers. As far as I'm concerned, PS does not support masks unless it is on smart object. Affinity Photo and Krita support layer mask, and for Krita, it supports nondestructive layer effect.