Why do cats and dogs have claws?

Cats and dogs are predators, but they use their claws for different things.

A cat's claws are very sharp and curved and can be retracted (except for the Cheetah, who cannot retract its claws). A cat uses its claws for many different things; climbing, self-defence, gripping hold of prey and other items (toys for example in domestic cats). They will retract their claws when walking, running or resting to prevent any damage being done to the claws.

A dog's claws cannot be retracted like a cat's can, and their main use is for gripping the ground while walking, running or chasing prey. A dog primarily uses its mouth and teeth to grab hold of prey and bring it down, for defence, and as various means of communication.