VG is vegetable glycerin
PG is Propylene Glycol (hospitals use PG vapor to deliver inhaled medications)
PG is thin enough for all methods of vaping, lets through the most flavor, nicotine Th and nicotine irritation, makes thin vapor
VG is thick (even thinned it is too thick for some methods of vaping), dulls everything PG lets through, makes thicker more persistent vapor
Most people use blends