Spread betting platforms essentially offer you a spread to trade, where the broker usually wouldn't be sending your orders to any exchange. Most of the spread betting or CFD platforms, the broker is becoming your counter party. So essentially it is like a video game mimicking the price of the underlying exchange, if you make money the broker loses and if you lose the broker wins. Also, it becomes very easy for this one broker to offer anything that is trading around the world on this platform. The broker offering you the platform bets on the fact that only a few win.
Spread betting/CFD's are banned in many countries including India. Check this, have given links to RBI circular that clearly states that if money is sent abroad, it can't be used to trade in any leveraged products.