What is a stock?

A stock is a piece of ownership in a company.When a company needs to acquire extra money to help grow the business, they can sell some or all of the ownership of the company in the form of stocks. So if you were to buy 100% of a company's stock, you would own the whole company. If you own enough stock you also have some decision-making power within the company. Buying stock is a very popular form of investing.