1. Different USES
A hammer is usually used to hit something, to deform or move an object by hitting it, or to pull a nail.
A mallet is used to hit something, but not a metal object.
2. Different shapes.
The hammer is shaped like a T. It's usually the handle plus the top. The top comes in a variety of shapes, from animal horns to wedges, and special ones to circles. The head was made of iron and had a handle perpendicular to the head.
The mallet is linear and bulges at one end.
3. Different application scenarios
Hammers are mostly woodworking tools. Often used for nail pulling and minor damage, the narrow, flat side of the hammer head concentrates all the force in a small area, which is best for driving nails. Rounded heads, on the other hand, are more ductile than pointed heads, which tend to crease or tear metal.
The mallet is mostly used for kitchen utensils or laundry. In ancient China, it was a wooden pillar with silk foil.
4. Different materials
Hammers are usually made of metal.
Mallets are usually made of wood.
