From Binary Options Wiki
These types of binary options are comprised of not just a single stock but of an index of many stocks, giving the trader diversification and opportunities to trade in particular sections of the market on a larger scale.
The market exposure index options give the investor is a winning tool and their growing liquidity is proof of this.
he simplicity of trading in index options comes without having to deal with individual stocks in several different transactions. Instead you are trading on a single index option such as the S&P 500 which includes 500 leading US companies, offering to be useful for those investors who have an idea of where the markets are going but who don’t wish to get too involved in the finer details.
Other index options include the likes of the FTSE 100, Nasdaq, IBEX 35 and the Dow Jones, all of whose price movements are easy to follow in daily worldwide financial news reports, another selling point for index options.