Your house's electrical system uses several parallel circuits to distribute electricity separately to various parts of the house. One circuit can go out without affecting others. If part of your house loses electricity, you may not have a serious electrical problem. Do not call a professional until you have taken some troubleshooting steps to determine whether you can fix the problem yourself. You may just have a circuit breaker issue or a problem on a ground fault circuit interrupter (GFCI) outlet. You may have GFCI outlets in your bathrooms and kitchen.
Flip off all of the breakers in your circuit breaker panel. Don't forget to turn off the main breaker afterward. This will reset the breaker switches and may resolve any problems you may have with contact within one of your breakers.
Turn the breakers back on. Check your house to see if any rooms still are without power. If you find a room without power, you may have a bad circuit breaker that needs replacement. Call a professional electrician if that turns out to be the case.
Check on any rooms that have GFCI outlets. These outlets have a red and black button in the middle. Plug an electrical appliance into a GFCI outlet, and press the "TEST" button. The appliance should turn off. Press "RESET" to turn the appliance back on. Do this at every GFCI outlet in the house. Eventually, you may find an outlet that caused your problem. Pressing "RESET" on a tripped outlet should return power to the area the outlet controls.
Call an electrician if these troubleshooting steps have not restored the lost power. Do not attempt to fix your electrical wiring on your own.