Triacs are components that are widely used in AC power control applications, Able to switch high voltages and high levels of current, and over both parts of an AC waveform. This makes these circuits ideal for use in a plethora of applications where power switching is needed.
Useful in circuits for light dimmers for domestic lighting, and they are also used in many other power control situations including motor control and electronic switches.
This is a sensitive gate TRIAC (also known as a thyristor) with a 200V blocking voltage in a bread board friendly TO-92 package. Use a triac to control an AC load (like EL wire, small incandescent lamps, etc) from a DC source (like the GPIO on a microcontroller).