Gaussian surface

Gaussian surface is an imaginary surface that surrounds or encloses a charge. It's like an imaginary bubble. The idea of a Gaussian surface is that it's a way of calculating the electric field (or other physical property) due to the charge inside the imaginary bubble. The electric field of the charge is the same everywhere on the Gaussian surface so you can calculate the total electric field of the charge by multiplying the electric field on the Gaussian surface by the area of the surface.