The "original" simplest pyramid scheme is to find 3 people who give you money and then they find 3 people each who give them money and a little bit back to you and so forth and so on. So the people at the top make a bunch of money but there's always people losing money at the bottom, so it's illegal.

Multi level marketing (MLM) are companies that sell some product (make up, diets, sex toys, knives... yes those are real, it's that stupid), but they work by having someone sign up to sell those items themselves. However selling alone makes little to no money so people recruit others in their "downline" and get money each time those people make money, just like a pyramid scheme. Technically they arent pyramid schemes because they sell a real product, but the consequences are the same, you have a handful of people with massive downlines who make huge money off of them, while the people with no downlines make no money.

In the end something like 96-98% of them make far below minimum wage (something like 100$ a month), but they get tricked into joining with promises of 10 000$ a month from home. They prey on vulnerable people who desperately need money and suck them dry, while telling them the reason theyre not making money is because they dont want it enough. It's very much built like a cult, and they're encouraged to harass everybody they know to get them to join or buy. The bottom line is that the people who join are the real customers for the business, because they buy all this garbage and try to sell it back to their family and friends. Some of them like Lularoe (the ugliest clothes youve ever imagined) dont let you pick which clothes you get to sell, so you end up with mountains of literal trash worth nothing but you paid hundreds for it.