It measures only the equity component of a company's capital structure, and does not reflect management's decision as to how much debt (or leverage) is used to finance the firm.
A more comprehensive measure of a firm's size is enterprise value (EV), which gives effect to outstanding debt, preferred stock, and other factors.
The total market capitalization of all publicly traded companies in 2023 was approximately US$111 trillion.
If the closing price per share rises to $21, the market cap becomes $84 million.
The number of shares trading on the open market is called the float.