The claw hammer is a hammer - very similar to the farrier's shoeing hammer - with square or round face, of 300-900 gr, with a split pin. The claw is used to pull out nails (1).
To do this, the carpenter takes his hammer with the iron under his hand, places the nail in the tapered crack and pulls back the handle. Due to the force exerted on the joint, it is often reinforced by two springs.
See also this hammer of the carpenter. [MOT]
(1) The double claw - two claws one above the other - occurs only exceptionally (eg SLOANE: 99). It was probably used to pull out long nails.