Stock refers to the ownership shares [one of the equal parts into which the ownership of a company is divided] of a company that are available for purchase by investors. When individuals invest in stock, they become partial owners of the company and have the potential to earn profits if the company performs well. For example, if someone buys stock in a company that produces computers, they may earn money if the company becomes more successful.
Very Simple Definition:
Stock means owning a part of a company. When people buy stock, they become a little bit owners of the company and can make money if the company does well. For instance, if you buy stock in a computer company and it becomes more successful, you might earn money.