what is meant by dielectric constant???why polar solvants have high dielectric constant whereas non polar solvants has low??

a quantity measuring the ability of a substances to store electrical energy in an electric field ,or in simple words u can say its the ratio of the permittivity of free space to the permittivity of a substances . 
in the case of polar solvent it can dissociate into ions that means cations and anions , but non polar solvent which cannot able to disocciate , so, once dissociate the dielectric constant will going to be directly proportional with the no of ions , 
so, polar solvent have high no of ions , so, they have high dielectric constant value 
HOPE IT CLEARS ..