Skinning allows players to gather leather, Hides and scales by skinning certain mobs (beasts, dragonkin, Silithid, and, very rarely, humanoids). Not all mobs of each type can be skinned, e.g. birds cannot be skinned despite being beasts. Leather, hides and scales are used for leatherworking. Leather is also used for some blacksmithing, engineering, and tailoring recipes.
More information can be found on WoWWiki.[]