A pyramid scheme is a money-making club which promises, once you have paid a joining fee, that you can earn large amounts of money by recruiting new members. Because the number of new participants in finite, pyramid schemes must eventually collapse – and most participants will inevitably lose their money.
Consumer Direct has a nice list of typical claims scammers make to get you to join a pyramid. It shows the sort of social phychological techniques scammers use to exploit the vulnerabilities of victims:
Before you join a scheme, be aware that over 90 per cent of people who get involved in a pyramid scheme never get their initial investment back.