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 enables switching on and the other handles switching off. A thyristor with a single MOSFET in its circuit that can only be activated (like standard SCRs) is referred to as an MOS-gated thyristor.