Pyramid schemes are scams. They can look remarkably like legitimate business opportunities, but if you become a distributor for a pyramid scheme, it can cost you and your recruits - often your family and friends - substantial time and money.
Promoters of a pyramid scheme may try to recruit you with pitches about what you'll earn. They will try to convince you it will change your life, even get rich, by selling the company's products. It is a lie. Your income will be based on how many people you recruit, not how much product you sell. Pyramid schemes are set up to encourage recruitment to keep a constant stream of new distributors flowing into the business.
The Special Audits Unit has produced a pamphlet that explains more on Pyramid Schemes.