>>5705518you have lighten layers, most common is screen, named that way because it actually work like screen with projector, imagine projecting picture on a wall and then you add second projector, you cant make picture darker, you're adding light so can only make it brighter
darken layers like multiply work like transparent sheets of foil with stuff drawn on them, you add another sheet of foil on your paper to make it darker, you stack few of them and you have very dark image, it works like real life so its intuitive once you realize it.
then you have overlay layers which darkens and brighten at the same time, if you put 50% perfect middle gray layer over your picture there wont be any effect, but if you grab a brush and start adding white color then those parts are going to be lighter, when add black it make picture darker, this is used in photography editing as "light painting"
for every layer you can make a mask, a second icon appear next to layer its pure white, when you click that icon you will be affecting mask and not the layer, when you add black color to it you make that part of layer to disappear, you can once again use brush with black and white color here to cut thing out/reveal them back in, to go back to layer editing mode you need to click the layer icon and leave mask editing mode
that's pretty much 99% of what you need to know
there are channels, and vector paths but it would be more difficult to explain with just text and its not really something used by beginners anyway