Rainbow Six 3 is a tactical shooter game DEVELOPED by UBI. The game is a first person shooter based on Tom Clancy's best selling novel by the same name. The game has two expansion packs, Athena Sword and Iron Wrath. The plot of Ravenshield is fully explained by Wikipedia (Tom Clancy's Rainbow Six 3). Basically it is all about an elite anti-terrorist group called Rainbow Six, a team bent on foiling the Neo-Facist terrorists doing damages on South American oil interests and European financial institutions.
I consider Rainbow Six 3 as the last of the original RS generation game. After RS3 it all went downhill and the original concept and perhaps purpose of the titular Rainbow unit was lost. Somewhere between the idea of making them more of a mountain assault shock troops and a desire for getting to the wider audience. Rainbow Six 3 also have one thing: the plausible feeling that you are participating in scenarios which are based upon real possibilities some which are unique like hostage rescue ops in Congo posing as Belgian paratrooper commandos. Overall, it rocks.