Market capitalization, sometimes referred to as market cap, is the total value of a publicly traded company's outstanding common shares owned by stockholders.
The New York Stock Exchange on Wall Street, the world's largest stock exchange in terms of total market capitalization of its listed companies
A public company is a company whose ownership is organized via shares of stock which are intended to be freely traded on a stock exchange or in over-the-counter markets. A public company can be listed on a stock exchange, which facilitates the trade of shares, or not. In some jurisdictions, public companies over a certain size must be listed on an exchange. In most cases, public companies are private enterprises in the private sector, and "public" emphasizes their reporting and trading on the public markets.
The New York Stock Exchange Building in 2015