How is this different from the electric motor?

First, the source of energy is different. The electric motors use electric current (electricity) and the electric generators use one of many energy sources but not electric current (electricity) to make wheels move (in a rotational motion) which move coils of wire around within an magnet field.

Second, the result is different. The electric motors make electric powered machines move and the electric generators make electric current (electricity).

Summary: Electric motors use electric current (electricity) to make things go (motion) and Electric generators use other energy sources to make wheels move (in a rotational motion) which move coils of wire around within a magnet field.