R and S enantiomers differ in:
Enantiomers are stereoisomers that are non-superimposable mirror images. A molecule with 1 chiral carbon atom exists as 2 stereoisomers termed enantiomers.
Enantiomers differ in their configuration (R or S) at the stereogenic center. It basically depends on the rotation of PPL. If one is Dextro-rotatory then other will be Laevo-rotatory.