What is a dewclaw in relation to dogs?

A dewclaw is a vestigial digit of the paw. It grows higher on the leg so that in digitigrade species, when the animal is standing, it does not make contact with the ground.Dogs almost always have dewclaws on the inside of the front legs and occasionally on the hind legs. Unlike the front dewclaws, the rear dewclaws tend to have little bone or muscle structure in most breeds. There is some debate about whether the dewclaw helps dogs to gain traction when they run because, in some dogs, the dewclaw makes contact when they are running and the nail on the dewclaw often wears down in the same way that the toenails on their other toes do, from friction with running surfaces. However, in many dogs, the dewclaws never make contact with the ground; in this case, the dewclaw's nail never wears away, and it must be trimmed to keep it at a safe length. It is notable that the dewclaws are not dead appendages. They can be used to lightly grip bones and other items that dogs hold with the paws.