Try running a search, or if you want to know what it is and how it works try www.howstuffworks.com . Other than that I can't really help you, all I know is it stands for Limited Slip Differential and its located at the joint between the axle and the drivetrain. I think its some sort of one-way gear mechanism.
Search on the Settings And Tunings board. Put "LSD" into the box and search that board only, and titles only. There are several good threads about limited-slip adjustment there.