The most common reasons for electricity to trip include having too many things plugged in, a faulty fuse or breaker or a wiring short. The trip occurs as a protective mechanism because it prevents too much current from flowing through a circuit.
If someone resets a breaker and nothing else happens, this likely means that the circuit has too much load, so unplugging a few things can help to prevent this in the future. The load a breaker handles can be determined by looking for the number on the breaker and looking at the maximum amperage rating. If the amperage exceeds this number, the breaker tips to avoid overheating. Since there are usually multiple outlets on a single breaker, it is easy to overload it. The number of electrical devices plugged in, including any light bulbs, can be looked at before adding up the wattage for all appliances and dividing by 120 to determine the overall load. In the case of a faulty breaker or fuse, replacing this prevents the issue, but care should be taken to make sure that it is just a single fuse or breaker, or the electricity will trip again. A wiring short is a very serious issue and can result in an electrical fire, so if there is a short, the homeowner should not reset the breaker until someone fixes the issue.