Normalizing income statement - gaap to non - gaap

Hi,

I came across with normallization of accounts (rather Income statement). It is something like converting GAAP to non - GAAP.

I just want to know as to:

What excatly it is?

How it is done? 

Why it is done?

When it is done?

Is it done in Indian accounting statements of the companies too?

Please advise.

Would be really grateful

Thanking you.