Wild yaks stand about two meters tall at the shoulder and domesticated yaks about one meter. Both have long shaggy hair to insulate them from the cold. They eat grasses, lichens and other plants. They are insulated by dense, close, matted under-hair as well as their shaggy outer hair. Yaks secrete a special sticky substance in their sweat which helps keep their under-hair matted and a acts as extra insulation.

The Yak is native to the hills, mountains and plateaus of south Central Asia, Tibetan Plateau and Mongolia in elevations between 3,200 meters (10,500 ft) and 5,400 meters (18,000 ft). In Tibetan, the word yak refers only to the male of the species: a female is a dri or nak. In most languages which borrowed the word, yak is usually used for both sexes

Domesticated yaks are kept for their milk, fiber, meat and beasts of burden. Their dung is even burned as fuel. Wild yaks form groups of 10 to 30 animals. Many wild yaks are killed for food by the Tibetans and are now a vulnerable species.