If the power has gone out in a single room or your whole house. It is most likely a tripped breaker switch. Blown fuses are increasingly uncommon as all new house construction as well as most older houses have been retrofitted with circuit breakers. fuses are just removed and new ones are screwed in, exactly like a light bulb. Tripped breakers are reset in a totally different way.
First turn off or unplug all the lights a electrical devices in the effected room or through out the whole house if you have totally lost power.
Locate your breaker box. It can be located on the outside of the house, inside the garage, in a closet or utility room.
Open the box, and you may need a flash light, so have one handy. You will most likely see a bunch of switches. Check them all and see if any are in the "off" position, or in the middle position. Once you have located the tripped breaker. Click it all the way to the "off" position, then click it all the way to the "on" position. It works similar to a wall switch in the house.
Wait a about 20 seconds to see if it will trip "off" again. If it stays on you have reset the breaker switch and you are ready to go back and turn on the lights in the effected room.