Locate your breaker box, usually a silverish metal in color. Open the metal door and search for a bank of switches organized in rows. Look for the breaker whose switch lever has moved from the ON position to the OFF position. The majority of circuit breakers include an orange or red marker window that indicates when they have tripped.
To rejoin your circuit and restore power, turn the switch to the ON position. This reset process may entail pulling the breaker lever all the way to the OFF position and then back to the ON position with some circuit breaker types. As the breaker clicks to the ON position, you will sense resistance in the lever, followed by a characteristic clicking sound or feeling. Turn on lights and appliances one by one along the circuit while someone stands by the breaker box to watch whether the circuit breaker trips again. If it happens, it's time to consult an electrician since it means the circuit has a more significant problem.