Stocks, also known as equities, are securities that represent an ownership interest in a company. When you buy a stock, you are buying a small piece of the company, and you become a shareholder. As a shareholder, you are entitled to a portion of the company's profits, as well as a say in how the company is run (although this is typically limited for small individual investors). The value of a stock is determined by the supply and demand for the company's shares on the stock market. If the company performs well and its profits and prospects for the future look good, the demand for its shares may increase, which can cause the stock price to rise. On the other hand, if the company performs poorly or faces challenges, the demand for its shares may decrease, leading to a drop in the stock price.