sorry. old chemistry term, referring to the "tetrahedral" shape of the "normal" bonds of a carbon atom. In the simplest organic molecule (methane -CH4) Carbon sits in the "center" of a pyramid, with 4 bonds at the three base "corners" of the pyramid and one at the apex. An enantiomer is a "mirror image" of the atom in question. Enantiomers are distinguishable in the way they rotate polarized light, with all "living" organic molecules rotating light to the left (or levo). Two enantiomers of, say, chloro hydro flouro methane would each have a chlorine, a flourine, an -OH group and a hydrogen attached at each "corner" but they are different atoms. There is no way they can be superimposed on each other, so although they are chemically identical, they are structurally different.
An enantiomerical image is basically the same...., except opposite, if you get the drift....
I can't believe I still remember that crap from 30 years ago. Haven't used it at all in over 15 years.