A stock exchange is a market that deals with the purchase and sale of securities. Securities are financial instruments that represent ownership in a company or organization. When a company wants to raise funds, it can issue securities, such as stocks or bonds, which can then be bought and sold on a stock exchange. Investors can buy securities as a way of investing in a company, and they can sell their securities if they need to liquidate their assets. The stock exchange provides a platform for investors to trade securities and allows companies to raise funds through the sale of securities.