A Ponzi scheme is a type of investment fraud. It lures investors by promising high financial returns with little or no risk. But there's a catch: the returns aren't generated by any legitimate business activity. Instead, early investors are paid with money from newer investors.

Think of it as robbing Peter to pay Paul. The organizer takes money from Investor C to pay off Investor B, who was paid with money from Investor A. The entire structure relies on a constant stream of new cash to keep up the illusion of a profitable enterprise.

The scheme gets its name from Charles Ponzi, an Italian immigrant who became infamous for his scam in the 1920s. Ponzi promised investors an astonishing 50% return in 45 days by supposedly buying and selling international postal coupons. For a while, it worked. Early investors received their payouts and, thrilled with the results, reinvested and encouraged others to join.

Word spread, and money poured in. But Ponzi wasn't actually running a real business. He was just using the flood of new money to pay the initial investors. This created the appearance of a wildly successful venture, drawing in even more people. The whole thing was a house of cards.

A Ponzi scheme needs an ever-increasing flow of new money to survive. As soon as the number of new investors slows down, or when a large number of existing investors try to cash out at once, the scheme falls apart. There's simply not enough money to go around because no real profit is being generated.

This is the core weakness of every Ponzi scheme. Mathematically, it cannot last forever. Once the flow of new cash dries up, the operator can no longer meet their obligations, and the entire fraud is exposed.