Stock market-linked investments have the potential to earn great returns, and offer savers the chance to make a lot of money if they are prepared to risk their capital and the market reacts in their favour. It is possible to invest in the stock market and earn returns tax-free, or invest in a portfolio which is carefully monitored by independent advisers and adheres to strict government rules. Many stock market-linked investments are linked to a stock market index, such as the FTSE 100, which tracks the success of the one hundred most valuable UK companies: if one company's stock falls, the index will be protected from falling by the success of other companies.