pls help me

I presume you meant VAT. Goverment uses tax as a revenue generating tool as well as to protect the economic interest of the country. Among the many factors, in order to be competitive in the global market Export of goods out side india is exempted from VAT and thereby price of the Indian goods becomes cheaper in the global market. Further export of goods is the main source to yield foreign currency.

In order to protect the domestic market, import of goods into India is charged to tax in most of the cases.