hi saurav,
They are saying that they have bought "A CONTRACT" of NIFTY Futures (contract) or MINIFTY Futures (contract)
Futures is a derivative product (
http://www.investopedia.com/terms/d/derivative.asp) where the price of the Future contract depends on the Nifty value.
Example:
Nifty is at 4500 (which we can't buy/sell), and
nifty future (which we CAN buy/sell) 1 month contract is at 4510.
The futures has a lot size (number of shares) fixed at 50. So, if you own/buy 1 futures contract then you are holding 4510x50 = 225500 amount of contract.
if nifty moves up say 1 point we get 1x50 = 50 rs and if it falls 2 points we lose 2x50 = -100.
Futures are leveraged product (you can own big quantity by depositing small amount), So, we can buy 1 nifty futures at 10% to 30% (based on market volatility) of the total amount. 225000 to 676500.
Try to avoid futures. it's very risky product to trade.
Please see derivative section for better understanding...