The Stock Market is where you buy, sell, and trade stock. There are many different Stock Markets around the world. The most important are the New York Stock Exchange, the London Stock Exchange, and the Tokyo Stock Exchange. All of them are always changing and are always busy.
The Stock Market changes in price. If you buy stock from a company and that company sells a lot of products, the stock price from that company goes up. If you buy stock from a company and the company sells lest products them then selled before, the stock price goes down. Many people do not understand the Stock Market. It is not just a person pushing buttons thinking "I think this Stock should go up today." It is people buying products from different companies that makes the price of stocks change. For instance, Nintendos stock was booming because of people buying merchandise from the cartoon, Pokemon.