An induction hob uses a changing magnetic field to heat compatible cookware directly. Many cast-iron and magnetic stainless-steel pans work; ordinary glass, copper and aluminum need a suitable bonded base or other manufacturer-approved design. A magnet sticking to the base is a useful first compatibility check.
The hob can still become hot from contact with the pan. Fast power response helps with simmering and boiling, but the pan's mass and construction also affect control.
Reference: Further reading.