This is your basic 3 hole outlet.
We have all seen the different kind of outlets that are in our walls. They seem to be different wherever you go. A lot of people wonder why there are three on some while there are only two on some others. On the outlets that have three holes, two of them actually go to the same source. The one on the left and the one on the bottom are the neutral and ground wires and when you follow them you realize they go to the same place.
Most appliances that are made of metal use the three prong electrical cords. These would be toasters, computers, stoves, refrigerators and such.
The third prong on these devices is to protect you from the appliance itself.
Here is an old 2 hole outlet. You probably wouldn't want to use this one!
On rare occasions, there is a wire inside that may come loose and start to conduct electricity along the metal surface. This wouldn't be good for anyone that might touch it. That third prong eliminates that issue from happening.
It accomplishes this by being connected to the shell of the appliance and it goes through the outlet and down into the ground.
Any current would be directed down there instead of through your body.
This would take that current, even if it's running through the shell of the appliance, and lead it away.
This way even if you touch it, you would still be safe.
Johanes Randy Prakoso
Some people remove this bottom prong if they don't have a three holed outlet, but you should know that it's very dangerous to do so.
If that current has nowhere to go, you could be electrocuted.