Earth: 
Its for protect the human beings from electrical shock due 
to any short conditions.Besides having low resistance 
bath....Earth can act as neutral,but neutral cant.

Neutral:
 Its return bath of Supply,it cant do the duty of earth.....

yes iagree this answer

earth and the neutral are two different things.

Earthing  mean connecting of non current carry mettalic 
parts directly to the great mass called earth.
and we found it every where.

While on the other hand 

Neutral we have to create it.
for a star connection we get it from the point where all 
the phases balances each other.
and for delta connection (if reqiured) we create it by 
using zig-zag transformer.

1. Earth is used in ac circuit for improve voltage capacity
Neutral is used for completing the path.
2. Earth is used as a neutral but neutral can't use as 
earth.

Neutral provide us the return path for the power to 
complete the closed circuit.

While the Earth is used to connect non current carrying 
metallic parts to it to protect us from the leakage or 
induced current due to generator action between the non 
current carrying metalic parts and near by A.C. coil or 
inductor.