A circuit breaker is a resettable switch in the electrical panel that automatically cuts power to a branch circuit when current exceeds its rating, such as 15 or 20 amps, or when a short circuit occurs. A thermal element trips on sustained overloads and a magnetic element trips instantly on shorts, protecting the wiring from overheating.
Why it matters to you
A breaker that trips once may only mean too much was running on one circuit, but one that trips repeatedly, feels hot, or will not reset is warning of an overload, a short, or a worn-out breaker.
Practical guidance
To reset, unplug the loads on that circuit, push the handle fully to OFF, then back to ON. If it trips again right away, leave it off and call an electrician, and never swap in a larger breaker to stop the tripping, since the wire size sets the breaker rating.