It is nitpicking, but in legal terms you could say he has shares in the company but not stocks. Stocks refers specifically to publicly traded shares, that is to say shares sold on a stock market. Shares is the more broad term as it can refer not only to stocks but also private equity units of various types. Valve is a Limited Liability Corporation, or LLC, which have Membership Units as the type of shares held by owners, which differs from stocks both in terms of tax treatment and limitations on how they can be transacted.