A breaker trips to protect you — it cuts power when a circuit draws too much current. Resetting one is simple, but a breaker that trips repeatedly is telling you something and shouldn't be ignored.
Reset it
Find the breaker that's flipped to the middle or off position in your panel. Push it fully to off, then firmly back to on. Power should return to that circuit. If it won't stay on, stop and investigate rather than forcing it.
Why breakers trip
The common cause is overload — too many appliances on one circuit, like space heaters and a microwave together. Unplug some devices and spread the load. A short circuit or a ground fault will also trip a breaker and is more serious.
When to call an electrician
If a breaker trips immediately every time you reset it, trips with nothing obviously plugged in, feels warm, or you smell burning, turn it off and call a licensed electrician. These can indicate a short or failing wiring that's a fire risk.