BT136 is a 600V 4A very sensitive Triac in a TO-220AB plastic package intended for use in general purpose bidirectional switching and phase control applications, where high sensitivity is required in all four quadrants. This very sensitive gate "series D" triac is intended to be interfaced directly to microcontrollers, logic integrated circuits and other low power gate trigger circuits.
TRIAC also known as Thyrister with a 600V blocking voltage. Use a triac to control an AC load (like motor, light, fan and switching etc.) from a DC source (like the GPIO of a microcontroller). Triac is a simple switch for AC, this triac can ve controled bt TTL levet microcontroller.