Editor's note: Abbreviations are really common in the hobby world, so I will present the full name followed by the abbreviation in parantheses.
Legend of the Five Rings (L5R) is a license owned currently by Wizards of the Coast (WotC). Alderac Entertainment Group (AEG) is in the process of buying the license back from them. It was originally made by Five Rings Publishing Group (FRPG), which was owned (and run) by basically the same people as Alderac Entertainment Group (it was a combination of AEG and Isomedia Entertainment.) Wizards of the Coast purchased FRPG, and in doing so, got the license.
The world of L5R is Rokugan, which is based on a combination of feudal China, Korea, but mostly Japan. There is also a region to the West, The Burning Sands, which is based on the Middle East. Of course, being written by a group of modern Westerners, it's filled with many anachronisms and cultural incongruancies. Some are intentional (women, in Rokugan, are equals to men, and can hold any of the same positions), but some are quite unintentional mistakes. (They accidentally named a family of the Unicorn Clan "Otaku," which apparently meant "lifeless geek." They later renamed them to "Utaku." In addition, the symbols that they used to represent the elements, which they going to originally placed on the back of the second generation of cards, spelled out "This game is not worth playing." Since then, they've fixed that as well.)
Originally, the L5R license was used for a Collectable Card Game (CCG), which is what most people know L5R to be. They later produced a roleplaying game (RPG). Then they produced a miniatures wargame. Fantasy Flight Games produced an L5R themed version of their Diskwars disc-based wargame, under license. Finally, a series of novels has been produced by Wizards of the Coast. (Which I recommend, they tell the story in an entertaining fashion, even if they occasionally disagree with the "canon" facts.)
Also see John Wick, Ree Soesbee, Andy Heckt, Rich Wulf, and Shawn Carmen, who have all contributed to the storyline of this world.