GFCI... Ground Fault Circuit Interruptor. Well, it does prevent you from getting "between line and load". As little as 5 milliamps difference between hot and neutral will trip the circuit. It's very existance is to protect you from getting fried.

GFCI locations... bathrooms, washrooms, outdoors, garages (USA, not in Canada), above counters for sinks and wet bars, unfinished basements (except sump pump or refigerator), crawl spaces, rooves, boat houses, swimming pool equipment, whirlpool baths, jacuzzis, exterior within 6.5' of grade (8' in Canada... must be for our bigger bears).

All houses in the US are wired 220V (240V) at the entrance. The 110 V is gained from splitting the 220V.

Anyone using the newer arc protection stuff? I don't know if it's mandatory yet or not in Canada.