A duplex receptacle has removable metal tabs that electrically connect line and neutral together on each receptacle. A split receptacle is a duplex with one or both tabs removed to isolate each receptacle from the other.
Switches are used to turn lights or electrical devices on and off. Usually when a switch fails, a light or electrical device will not turn on. After determining that a light bulb is not burned out and a circuit breaker or GFCI is not tripped, the switch may have failed.
Circuit breakers protect a circuit from overloads and short circuits. When the current exceeds the rating of the breaker, it will trip. Circuit breaker ratings for household use are typically 15, 20, and 30 amps.