Note: Triple Battles are only available in Pokemon White Version but you could find one or two in Pokemon Black Version. You will be able to find one or two Rotation Battles in Pokemon White Version but they are mainly in Pokemon Black Version.[1]
Triple Battles are battles where the first three Pokemon in your party are out to battle at the same time which is quite cool. Here's a recommendation for your first three Pokemon after you've finished the main story: Zekrom(Reshiram in Black)Level 70, Emboar/Serperior/Samurott Level 75, Kyurem Level 60-70. But that's only a recommendation. When you lose one of the three Pokemon, you have to replace it with another Pokemon. When you win, all three Pokemon get the experience. Also if, for example, Zekrom uses Fusion Blast on a Pokemon and Kyurem aims for the same Pokemon, Kyurem will just attack the next Pokemon along the line. That's it! You're details on Triple Battles in Pokemon White Version even though I only have Pokemon Black Version.