Stocks are shares of ownership in a corporation. When you buy stocks of a publicly listed company, you become a stockholder or shareholder of a company. In other words, you become part-owner of that company. 

As such, you participate in that company's growth and future profits. Conversely, you may also lose if the company suffers a loss or performs below market expectations. 

Note: It is also known as a Share, Equity or Security.

To watch a video on how to have an investing mindset, click here.