the above answers are good info
PG - thinner more watery - more throat hit, more taste, better wicking, less burnt taste
VG - thicker liquid - more VG = more vapour, less taste and depending on PV used may help with LESS LEAKING, but too much may cause wicking problems leading to more burnt tastes
So a mix of these is usually used... I prefer 60/40 VG/PG... but having some PG and VG on hand to adjust your eLiquid would be handy