HTC's market cap recently passed RIM's -- currently at $28.5 billion -- and this week edged out Nokia's, now at $32.8 billion. The company has been building and selling smartphones roughly as long as Nokia and RIM, but its early embrace of Google's Android has helped it grow to have a market value 30 times what it was five years ago. It has also chosen to support Windows Phone, but this new platform has yet to prove itself.
Market capitalization is the share price times the number of shares outstanding (shares that have been authorized, issued, and purchased by investors) of a publicly traded company. It is the public's opinion of a company's net worth, and is one of many ways to measure how a business is growing.