What is the significance of Gauss' theorem? Is it applicable to any other fields other than electric field?

Explanation

If the electric field intensities at all points of a closed surface are known, then whit the help of Gauss' theorem, the amount of charge responsible for creating the field can be found out. Again if the charge enclosed by a surface is known, intensities at various points on it can be calculated.
This theorem is also applicable for conservative fields, like magnetic field and gravitational field.