horn structure which surrounds the distal phalange in odd-toed ungulates (horses, donkeys and zebras)

A hoof is the foot of certain animals known as ungulates (such as deer, cows, pigs, sheep, and giraffes). These animals walk on their toes. The toes have a hard cover made out of the same material as fingernails. This is called keratin.

This is a giraffe hoof.