A dog's paws are his hands, feet and shoes all in one. Every type of dog has a slightly different paw structure, although they are all similar anatomically speaking. Dogs are more like horses than people when it comes to walking. They walk up on their toes, rather than the soles of their feet. Their walk may be different from humans, but the bone structure of the canine paw is very much the same.
A dog's paws are the shock absorbers of his foot and pastern (wrist). A dog is not as deft as a cat with his paws. He cannot clean himself or "grab" his prey like a cat can. Rather, a dog uses his paws to dig and scratch. Walking and running are really the best uses for a dog's paws.
Not all dog's paws are the same. Some dogs, like the field breeds (keeshonds, Akitas, doberman pinschers), have "cat-like" feet that are very compact and don't require as much energy to lift. Other dogs--like a Chesapeake Bay retriever, Portugese water dog or field spaniel--have webbed paws that help them swim and retrieve water fowl.
A dog's toenails, or claws, are unlike a human's in that they are very thin and placed toward the inside of each of a dog's four toes. The toenails are important for giving a dog a grip on a slippery surface, scratching at the ground and, sometimes, tearing into his dinner. A dog's toenails should be kept trim; otherwise, they can tear and rip, causing the dog great pain. A dog's nails might stay trim on their own if he exercises regularly on pavement or concrete. A dog who spends most of his time on grass or dirt will need to have his nails trimmed. Many dogs have a fifth nail and pad on the inside of each pastern, called a dewclaw. This claw isn't of use to the dog, although there is speculation about how it might historically have been used by various breeds. To prevent the claw from ripping and hurting the dog, dewclaws are often removed when a puppy is very young.
A dog's toes are not unlike human fingers. The bone structure is the same, but the use is different. A dog walks on his toes, and the bones remain at an almost 90 degree angle when he is standing up. A dog cannot move each toe independently--as a human can move a finger--which limits what a dog can do with his toes.
There are five pads on a dog's foot. One is on each of the four toes, and a larger pad is centred in the "palm" of the foot. Pads vary in style almost as much paw structure. Pads can be smooth or rough, large or small, thick or thin, depending on the dog and what it was bred for. A dog with a thick, rough pad might have historically been more of a working dog than a dog with a thin, smooth pad. The pad is the dog's shoe. It is his only protection between himself and the ground.