R-ALA, S-ALA, Thioctic Acid? What is the difference?

Here's some information on your question from Oregon State University Linus Pauling Institute - Micronutrient Information Center:

"Lipoic acid (often called α-lipoic acid), also known as thioctic acid, is a naturally occurring compound that is also synthesized by humans." (Summary section) - https://lpi.oregonstate.edu/mic/dietary-factors/lipoic-acid

"Lipoic acid also contains an asymmetric carbon, which means that lipoic acid can exist as one of two possible optical isomers, also called enantiomers. These enantiomers are mirror images of each other: R-lipoic acid and S-lipoic acid (Figure 1). Only the R-enantiomer is endogenously synthesized and covalently bound to protein. R-lipoic acid occurs naturally in food (see Food sources). Free (unbound) lipoic acid supplements may contain either R-lipoic acid or a 50:50 (racemic) mixture of R-lipoic acid and S-lipoic acid (see Supplements)."
-- Same link as above only near the bottom of the page in the Introduction section.

@johnbishop
Thank you John!
Much appreciated!