No electricity to half the house
Assuming you are in North America, this probably indicates as problem in the main circuit breaker. Basically, you have two legs of 120V each with opposite phase so that when used together, you get 240V. Half of your 120V circuits are on one leg, the rest are on the other and 240V circuits (stove, furnace, etc.) are on both.

Probably one half of the main breaker isn't conducting. Try turning the main breaker off and on a few times to see if you can make it work.

Even if you get it working, you need to call an electrician to replace it.