What is a power thyristor, Current controller, triac circuits, triac thyristor

 BTA12 Series 600 Vdrm 12 A Flange Mount Snubberless Triac - TO-220AB

https://www.futureelectronics.com/p/electromechanical--circuit-protection--power-thyristors/bta12-600bwrg-stmicroelectronics-6124363