Ans. Statement: The total electrical flux through a closed surface is equal to $\frac{1}{\varepsilon_{\circ}}$ times the total charge enclosed by the surface $${\phi_{_E}=\oint\overline{E}.\overline{ds}=\frac{1}{\varepsilon_{\circ}}q}$$
Importance:
1. Valid for any closed surface of any shape and size.
2. Applicable to any distribution of charges within the closed surface.
3. It is useful towards a much easier calculation of electrostatic field when the system has symmetry.