Anything about the stock market?
Essentially all the companies listed are publicly traded forms of a joint stock company. Whereby the company is run with the shareholder's interests in mind. The companies issue shares at a certain price to raise capital and people either buy it and drive up the price or they don't. There's different kinds of shares, but they all basically confer partial ownership of the company which is why you can sell your shares to other people in speculative efforts. Anyway, could write 10 pages about it so look on wikipedia for further clarification. I'll just say there are other regulations like Mutual funds can only own a certain percentage of companies which prevents billion dollar funds from engaging in takeovers.