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Originally Posted by clickhappy I don't understand what grounding it means

In single phase grounded electrical systems there are 3 wires: ~phase, neutral and ground (black, white and bare copper), all of the bare copper connect to a terminal in the breaker box then go out of the building via a cable to a steel grounding rod pounded into the earth.

If there is a short and the power cord of the device is grounded; the electrical current takes the path of least resistance -- to the ground as the earth has less resistance than the human body or the device plugged in. If there is a short in the computer it usually fries. I have heard of many computers fried even when they were on a surge protector (the condom broke...).

If lightning hits your house's electric system the 50,000 volts goes thru to the grounding rod and you don't fry and burn from the resulting electrical fire.

On 120V systems, 3 wire grounded power has been code since the late 1960's.