Valve is one of the top video game developers and publishers in the market. Some of their more popular titles include: the Half-Life series, the Left 4 Dead series, Counterstrike, the Team Fortress series and Portal. Valve is also well known for their content delivery system and online store, Steam. Valve developed Steam as a means of digital distribution for their games. Their hope was to provide not just a store but an application that could easily update games and allow for player communication. After a somewhat rocky start, Valve's program established itself as a major video game store. Steam now has deals with most major publishers and releases games simultaneously with retail releases. Valve has also developed its Steamworks system to provide Steam based achievements and communities for non-Valve games.
Read all about Valve as a company, reviews of games and more information at Steam.