Skinning is one of the key features of osu! that allows players to restyle the game's interface based on provided default elements. User-made skins range from fun-themed to professional-looking designs, or may be deliberately challenging or nigh impossible to play with.
Main page: Skin set list
For beatmaps only, if your beatmap skin contains a single element from the listed sets in the ranking criteria, it must contain all of the other elements within said skinning set. This only applies to beatmap skins, but other skinners are advised to follow these lists as well to preserve the integrity of their skin.
Skin elements are split up into several categories as follows: