In his book Saving and Investing, Michael Fischer writes:
Compounding our money with a return over a long period is the key to accumulating larger sums, but what is it that allows our money to receive a return, and what determines whether this return will be good or bad? [...] As savers and investors, a key way for us to compound our money is by directly or indirectly making our money available to users of capital. Users of capital can be companies or governments, who are looking for money to undertake projects or to buy something.
This relationship between providers and users of capital forms the backbone of our financial markets and our economic system. Before diving into the first of two parts on this topic, Michael explains why it's important to start here: