They have two MOSFETs of opposite conductivity types in their equivalent circuits. One is responsible for turn-on and the other for turn-off. A thyristor with only one MOSFET in its equivalent circuit, which can only be turned on (like normal SCRs), is called an MOS-gated thyristor.
These devices have two MOSFETs of opposite conductivity types in their equivalent circuits, where one facilitates switching on and the other handles switching off. A thyristor with a single MOSFET in its circuit, which can only be turned on like standard SCRs, is termed an MOS-gated thyristor.