VAT is a malty stage tax that means it is calculated each and every stage of a good and services. it is imposed at different stage of manufacturing and at final sale.
for example
If you take a product X what ever
the X is manufactured by company (whatever) ,for manufacturing this product X the company requires some inputs like raw materials and parts from other suppliers.For buying these inputs this manufacture want to pay a VAT.
So the manufacture of the product X has paid VAT for the inputs.
Therefore the VAT charged from the supplier side to manufacture is called Input Tax
Now the product X is completed so it is end product.
A consumer come to buy the product X
So now the consumer want to pay the VAT for this end product
It means the consumer payed the VAT on added value.
Here, the VAT payed from the consumer side to the manufacture that is called as Output Tax
So the VAT is calculated the different between the output tax collected at a time of sales and Input Tax paid at the time of Purchases.