You can buy and sell goods (ownership in companies) There is a shop keeper (a stockbroker) It opens and closes (fixed times every day) You cant control the price (you are a price taker)
Instead of eating the produce, you can sell them back (selling part of the company to somebody else) You cant walk into it, but you can window shop! (just like eBay) Nobody owns it!!
Name a few HUGE companies ( e.g. McDonalds) What do they sell? (e.g. millions of burgers) Think of how much money they make (e.g. billions) You can have a slice of the action by buying a portion of that company in the stock market