A stock is part ownership in a corporation. There are laws and rules that govern stock issuance and stock investing. You have proxy voting rights with many stocks. You can go visit the physical corporation which has a "book value" and you can determine worth based off that value plus revenue and earnings minus operational costs and decide whether you want to invest.

There have been stock swindles in the past--the 1800s up to the 1920s were full of them. There have been insurance and bond swindles, too.

High growth stocks may be bubbles, but are not pyramid schemes.