Under normal conditions a stock tranny will put the power to the axle that has the least resistance. Which really sux if one tire is in snow & the other on pavment & u'r stuck.. or if your at the race track & u have more power than the one wheel can put to the ground & u sit & spin.
The LSD tries to spin both axles regardless of the amount of resistance. Thus puting the most amount of power to the ground as possible.
i'm sure u've probly heard the term 1 wheelie pealie.. LSD tries to prevent that!