it's a way to group lots of layers into one thing. you can close folders and you wont see all the layers all the time until u open it back up again. it can also be move, like an example if I want to move Artline, coloring and shading layers without messing it up, I can put them in a folder and it'll move all layers at the same time. you can also rename it like layers by double clicking it. you can clip a layer on the folder and it'll work the same as clipping a layer to another layer.

as the title says but also so you can select multiple layers at once

having the option to create folders for your layers in the canvas for easy organization when together with others and at the same time being able to move a bunch of layers together

Make it possible to group layers in folders within a canvas if you want to separate different illustrations from the same canvas and need to toggle the visibility off without needing to merge the layers to keep the information of the separate layers that compose the drawing intact in case you need to modify them later and keep your list of layers organized.

I notice that when I draw with friends, the layers can become a bit messy. I think folders would be a nice way of keeping the layer section clean and easier to manage. Especially when drawing with a large group of friends.