To sculpt is to shape or carve a figure out of a moldable or hard material. You could sculpt a figure of your mom's cat or you could sculpt your biceps by lifting weights.
Artists who sculpt are called sculptors, and the work of art they make is called a sculpture. You can sculpt out of wood or stone, by carving, or sculpt clay by molding and shaping. You can sculpt metal by heating it and pouring it into molds, or by welding pieces of it together. It's even possible to sculpt with balloons, twisting them into complicated structures or figures.