The BT136 is a popular, general-purpose TRIAC (Triode for Alternating Current) used for switching and controlling AC power, known for its bidirectional switching capability, handling around 4 Amps at 600V (like the BT136-600D) in a TO-220 package, ideal for dimming lights, controlling motor speed, and static switching in home appliances and industrial settings, often triggered by low-power digital signals from microcontrollers.