Unity GUI questions

Hello everyone. My name is Cody and I have a question. In video games such as, call of duty, battlefield, rush team, contract wars, etc. Do they use GUI skins for menus and buttons and what not? If anyone could point me in the direction to learn, it would be greatly appreciated. Thank you.

Gui skins are merely parameters / textures for the gui of an entire project gathered into a file, which gives several advantages. Information is stored in one place, you can switch easily, you can have versioning etc.

Also I don’t know how big productions do it, but I bet it is something very similar. Might not be called GuiSkin though.