Fuses are an electrical device that blows when there is excess current. In this way, the integrity of the conductors is safeguarded, reducing the risk of fire and / or breakdown.
A fuse holder is an instrument used to safeguard the fuse inside it.
A thermostat is a device that automatically regulates the temperature to keep it at a certain level.
A Circuit Breaker, is a device used to interrupt the current when it exceeds a specific level (they can be found in the electrical panel of the houses)