Some people say that old games shouldn’t be kept alive, that they have gone out of style for a reason. Thankfully, Bethesda has a different opinion on that matter, and has now successfully revived Quake III as a downloadable, standalone first-person shooter. While Quake Live (as the remake is called) has been available as a browser game for the past couple of years, the developers got tired of having to keep up with the ever-changing browser plugins. Players will now have to download the client in order to join the arena and show off their player-versus-player skills.
Don't worry about losing the progress which you've previously unlocked in the free-to-play MMOFPS, as both the friend list and statistics will remain the same. Keep in mind that the standalone Quake Live version is for PC users only and won't support Linux or Mac.
If you don’t want to rely on other members of your team, then join Free for All and fight on your own; if you prefer teaming up with friends instead, step inside the Team Deathmatch arena; if you want to put your skills to the test by going up against one other player only, choose Duel; if you’re more of a pacifist and enjoy speed-running more than killing, join the Race team. Remember that this is just a selection of all available game modes. For more information, just hop into the game and relive the classic Quake 3 experience online.
Source: Official game homepage