can some one explain earth to me???

[aveekbh]

So could someone try to explain very basically what earth is that would be much appreciated.

This is how I understand it. The earthing system serves two purposes:

• In any mains-connected equipment, all exposed metal (i.e., the chassis) needs to be earthed. This ensures that any conductive surface is always at 0 volts. Thus, if you touch the metal, your hands and feet are at the same electrical potential, and you will not receive a shock.
  
• Should the chassis come into contact with live voltages, any shock can be fatal. Because the chassis is electrically connected to earth through a wire, a large current would flow through the earth connection. This should be enough to cause safety mechanisms to activate - fuses would blow or circuit breakers will trip - cutting off the supply, and keeping people safe.
  

Please feel free to correct me if I'm wrong. 

There are various ways in which the earth connection can be provided. This video will give you an idea about the systems in use in the UK, but the principles are the same everywhere.

These days, one should also have a residual current device which will also disconnect the supply if there is an abnormal condition. These are an additional safety feature, and should also be used in conjunction with fuses or circuit breakers.

Hope this helps 

[c4757p]

Neutral and PE are never connected in the house, only at the utility side where they are connected on the supply side of the electricity meter, along with an earth rod connection and bonding to water piping if metal. Inside they are required to be separate. Often they will be separate all the way back to a substation transformer bonding bus, which can be 200mm2 copper bar.

Again, depends on the country. The US has nearly one transformer per house, so we do things a bit differently.