The verb compound here means to grow and add quickly, not in a straight line but the growth itself is growing. The small advantage keeps becoming a bigger and bigger advantage. That's what exponential means, too. It's like compound interest in the bank. You earn interest on your deposit but if you leave that interest in the account, the growth itself will keep growing because the base amount (your principal) is growing thanks to the interest. http://moneytipcentral.com/wp-content/uploads/2008/06/compound-interest-graph.jpg