There's no shame in not knowing what a limited slip differential is. After all, every budding car guy has a first time trying to parse Brian Beckman's The Physics of Racing. (And many of us still don't understand the entirety of it after multiple perusals.)
So if you're trying to wrap your mind around just what this Torsen thing is, there's no excuse for not watching this new video from Scion. While it's basic, it does explain the rudimentary physics behind a limited slip in just two minutes. If nothing else, it should get you started in looking for some more comprehensive information.
Scroll down to watch the video.