Ok so meth,it has 1 chiral carbon. One carbon that turns a little if you were looking down the barrel of a gun. Imagine someone riding a bike toward you. They stick out their left leg. Then they stick out their right leg. That's the difference between L(eavo) and D(extro) meth. Racemic meth just means it's roughly a 50/50 mixture. That is what you get when you use a precursor that isn't chiral. Example include P-2-P, phenylacetone most thing ephedrine and pseudoephedrine ARE chiral though they hav2 c chiral carbons, but lose the first one in the reduction to meth. And the second one determines whether you make L or D meth using L and D is archaic though and the cool kids are using R, and S, like a rallysport racecar