The stock market is a complex system where shares of publicly-traded companies are issued, bought and sold.Its a collection of millions of investors with diametrically opposing views. This is because when one investor sells a particular security, someone else must be willing to buy it. Since both investors cannot be correct, it is an adversarial system.There are many factors that determine whether stock prices rise or fall. These include the media, the opinions of well-known investors, natural disasters, political and social unrest, risk, supply and demand, and the lack of or abundance of suitable alternatives.