Permittivity of an material is an electric property it has.
It determines the amount of electric field a charge can produce when placed in it.
Consider two materials with electrical permittivites
When a charged particle
For the second material the field due to the same charge at a same distance
So permittivity determines (in a sense) the ability of the medium to respond to electrical effects.
The permittivity of vacuum is denoted as
Thus, the electric field produced by point charge