The index is called the indicators that measure the proportional change in the prices, costs and sales performances of the investment instruments traded in Forex within a certain period of time. Nearly two hundred stock exchanges in global markets There are dozens of indices within its structure. Investors can buy and sell these indices. To give an example from the domestic BIST 100 index, like the BIST 30 index. Abroad, it is possible to count many popular indices from the S&P 500 to the Nikkei 225 index.