Outstanding shares refers to all of the shares of company held in total, which includes all ownership - retail investors, institutional, the company’s officers, insiders, and so on.

Outstanding shares are listed on the balance sheet under “Capital Stock,” and are used in calculating market capitalization, earnings per share, and other critical per share calculations. The amount of outstanding shares can fluctuate over time on the basis of corporate actions, such as share buybacks (reduces overall count) or new share issuance (increases overall count).