Securities are financial instruments that represent ownership or a creditor relationship with an entity. They can be categorized into two main types: equities, which include stocks that signify ownership in a company, and debt securities, such as bonds, which represent loans made to an issuer. Investors buy securities to earn returns, either through price appreciation or interest payments. Securities are traded on various markets, including stock exchanges and over-the-counter markets. The value of securities can fluctuate based on market conditions, company performance, and economic factors. Regulatory bodies, like the Securities and Exchange Commission (SEC), oversee the trading of securities to ensure transparency and protect investors.