A thermostat is a device that senses temperature and automatically regulates a system to maintain a desired setpoint. Found in everything from home heating and cooling systems to vehicle engines and household appliances, it acts as a closed-loop controller by turning heating or cooling units on and off, or by adjusting the flow of coolant fluid. Depending on the application, thermostats operate using mechanical components (such as expanding wax pellets or bending bimetallic strips) or electronic sensors like thermistors. By continuously monitoring environmental or fluid temperatures, a thermostat prevents overheating or overcooling, ensuring operational efficiency, safety, and comfort.