Market capitalization is the total value of the stock of a public company, as in the current price-per-share multiplied by the total number of shares owned. The largest market capitalization is usually a few hundred billion dollars or, the peak of a bull market, close to a trillion dollars. Market capitalization varies daily as stock values fluctuate.
Investors refer to market capitalization a way of assessing the attractiveness of a stock for purchase or sale. Large-cap companies have values of at least $10 billion, mid-cap companies have values between $2 ad $10 billion, and small-cap companies are worth between $300 million and $2 billion. Companies worth less than $300 million are called considered to be "micro-cap".