Leather is a material made by treating (tanning) the skin or hide of animals, usually cattle.
Leather is very strong, and may have a characteristic odour that some people like. Some, such as those into animal transformation fantasy, may like the fact that it is animal skin rather than artificial like PVC.
It is widely used for making shoes and boots, and also for making clothes. In a BDSM context, it is used for making various equipment including blindfolds, handcuffs, straps and whips. Leather clothing and other objects may be fetishes.
Leather that has not been fully tanned is called rawhide. Rawhide has the property that if soaked in water it can be stretched, and will then shrink as it dries out. It can thus be used to make bonds or clothing such as corsets that keep tightening (see Skin-tight clothing), or ropes that will eventually lift someone off the ground.
Leatherette is an artificial fabric intended as a substitute for leather. On the fetish scene, it may be a substitute for latex sheeting. It is made by covering cloth with a layer of plastic or rubber.