Circuit breakers are found in your home’s electrical box. If the current flowing into the various lights and appliances in your home grows too strong, it can short out the wiring and cause a fire. Circuit breakers will trip when the current reaches a certain level: shutting off power to that section of the house until the problem can be addressed. Malfunctioning circuit breakers need to be replaced with new ones, but you don’t need to call an electrician to test them. You can use a multimeter available at any hardware store and run a basic diagnostic on a circuit breaker very quickly.
Open the electrical box in your home. You should see a long row of black switches corresponding to a different part of your house. (Ideally, they will be labeled as such so you can tell which one goes to which part of the house.) These are the circuit breakers.