Market capitalization or market cap is the total dollar market value of the shares outstanding of a publicly traded company; it is equal to the share price times the number of shares outstanding. As outstanding stock is bought and sold in public markets, capitalization could be used as a proxy for the public opinion of a company’s net worth and is a determining factor in some forms of stock valuation. The investment community uses this figure to determine a company’s size, as opposed to sales or total asset figures.
Source: Wikipedia