What is electric flux? Detail

Consider a space in which a charge is placed. Now, the electric field lines will penetrate, let’s say for our reference, a surface at a certain distance away from the charge.

This surface could be thought to have electric field of its own although the charge produces it. Basically, this hypothesis was introduced to analyse the influence of a charge on the continuous planar surface surrounding it. This laid the foundation upon which Gauss formulated electric flux as E.dA (where E is the electric field and A is the area vector).