Learn the stock market basics from professionals. Understanding the stock market is a key to your success in trading and gives overall insight into how our society works. Understanding the stock market is a key to your success in trading and gives overall insight into how our society works. In a nutshell, the stock market is where investors can buy and sell securities, or investments, such as stocks, bonds, mutual funds, exchange-traded funds (ETFs) and cash equivalents like Treasury securities. Also known as a securities exchange, each market is subject to government regulation and has its own set of rules. How is a stock price determined by the market? By allowing millions of people to buy and sell shares of the company using the same set of information, it creates transparency and liquidity. Over time, this pushing and pulling creates a “fair” price for the stock.