Steam is Valve's new way of getting games into your hands ASAP. Games like Half-Life, Counter-Strike, and Counter-Strike Condition Zero are all being made available through Steam.
Steam games are automatically kept up-to-date with the latest content and revisions. Steam also includes an instant-message client which even works while you're in-game.
At its core, Steam is a distributed file system and shared set of technology components that can be implemented into any software application.
With Steam, developers are given integrated tools for direct-content publishing, flexible billing, ensured-version control, anti-cheating, anti-piracy, and more. Check out the full feature list, and install Steam today!