What is the purpose of the dew claw?

The dew claw is on the back of the front leg about an inch above the foot of a dog. Some people have them removed when the dogs are puppies. If not, you will feel a nail, just like a dog's toenails, protruding from that area. It is said that it is called the dew claw because it merely touches the dew on the grass as a dog walks.