A breaker trips when there’s either a short or fault in the system or when you’re using more power than the circuit has available. This could be due to having too many items plugged in, too many lights on, etc. Circuit breakers are designed to trip and turn off power when any of the following dangerous situations occur:
An overloaded circuit is the primary reason for a breaker tripping and occurs when a circuit is has more connected electrical load than it is supposed to have. When more current runs through the circuit than the circuit was intended to take, the circuit breaker is designed to, well, “break the circuit” and save your appliances.
The Short Circuit is a more serious reason for a breaker tripping. A short is caused when the hot wire (black) touches another hot wire or touches a neutral wire (white). It can also be caused if there is a break in a wire in the circuit. Shorts are a bit more difficult to diagnose because they can be caused by the wiring in your home or in something you have plugged into an outlet.
A Ground Fault condition exists when the hot wire (black) touches the ground wire (bare copper) or the side of a metal outlet box (because the metal box is connected to the ground wire). The ground fault is a type of short circuit.