Product-Based Pyramid Scheme Definition:

Pyramid SchemeA product-based pyramid scheme is an income opportunity, in which persons are recruited into a pyramid of participants making ongoing personal purchases or retail sales of products and services. These persons recruit others to do the same in an endless chain of recruitment and personal consumption or retail sales.  This is done in order to qualify for commissions and bonuses and to advance upward in the hierarchy of levels in the pyramid. Personal purchases or retail sales become the means of disguising or laundering investments in the product-based pyramid scheme.

Additional note:
Typically, prospects are lured into the scheme with exaggerated product and income claims. And because the pay plan is heavily stacked in favor of those at the highest levels in the pyramid, the vast majority of participants spend more than they receive and eventually drop out, only to be replaced by a stream of similarly misled recruits, approximately 99% of whom are likewise destined to experience loss and disappointment. – Source Research-based web site Mlm-thetruth.com

Modern pyramid schemes generally do not blatantly base commissions on the outright payment of fees, but instead try to disguise these payments to appear as if they are based on the sale of goods or services. The most common means employed to achieve this goal is to require a certain level of monthly purchases to qualify for commissions. While the sale of goods and services nominally generates all commissions in a system primarily funded by such purchases, in fact, those commissions are funded by purchases made to obtain the right to participate in the scheme. Each individual who profits, therefore, does so primarily from the payments of others who are themselves making payments in order to obtain their own profit. – Source FTC Division of Marketing Practices James Kohm

Pyramid schemes—also referred to as franchise fraud or chain referral schemes—are marketing and investment frauds in which an individual is offered a distributorship or franchise to market a particular product. The real profit is earned, not by the sale of the product, but by the sale of new distributorships. Emphasis on selling franchises rather than the product eventually leads to a point where the supply of potential investors is exhausted and the pyramid collapses. At the heart of each pyramid scheme is typically a representation that new participants can recoup their original investments by inducing two or more prospects to make the same investment. Promoters fail to tell prospective participants that this is mathematically impossible for everyone to do, since some participants drop out, while others recoup their original investments and then drop out. – Source FBI.gov

Here is an informational video on identifying and protecting yourself against pyramid schemes.

Pyramid Schemes Primer Video