it is likely that class B shares have a greater voting weight than class A shares. This is a traditional way to sell off part of the company while retaining control for the founders and initial investors.
more info: from Google's IPO filing:
Following this offering, we will have two classes of authorized common stock, Class A common stock and Class B common stock. The rights of the holders of Class A common stock and Class B common stock are identical, except with respect to voting and conversion. Each share of Class A common stock is entitled to one vote per share. Each share of Class B common stock is entitled to ten votes per share and is convertible at any time into one share of Class A common stock.http://www.secinfo.com/d14D5a.148c8.htmto give you an idea of the difference, when Google went public in June, 04, the following options were outstanding, the founders and CEO probably owned the 10,000,000 options of class B (they made $130 on each share):
•1,933,953 shares of Class B common stock issuable upon the exercise of warrants outstanding at June 30, 2004, at a weighted average exercise price of $0.62 per share.
•6,276,573 shares of Class A common stock issuable upon the exercise of options outstanding at June 30, 2004, at a weighted average exercise price of $9.42 per share.
•10,456,084 shares of Class B common stock issuable upon the exercise of options outstanding at June 30, 2004, at a weighted average exercise price of $2.68 per share.
•3,891,192 shares of common stock available for future issuance under our stock option plans at June 30, 2004.