why do people trade in stock

Gee! That sounds totally crazy. I would only do that if I was 100% sure the stock value would go up through the roof the next day. For that sort of thing to happen you would probably need insider trading imformation, which is illegal. But these people that do that are probably not involved in anything like that. They are probably compulsive traders (much like gambling). I used to trade on the stock market some time back - just for a year. Made around 40% profit! I learnt alot and it was pretty fun and very exciting. I only dealt with very small amounts of money which I could afford to loose. It was more an experiment for me. But to make real money, you also need to start of with more than a few bucks, which I don't have at the moment. One of the rules of trading on the stock markets is never use money you can't do without.