Linked from
The 19 pages that link to Divergence theorem, each with the reason it gives.
Surface integralRelated: It can replace a closed-surface flux integral with a volume integral.
Gauss's lawRelated: It turns the integral form of Gauss's law into a local differential equation.
Multivariable calculusRelated: It links local sources and sinks to boundary flux.
Volume integralRelated: It converts certain volume integrals into boundary flux calculations.
Poynting's theoremRelated: It converts the local flux term into energy crossing a region’s boundary.
Gauss's law for gravityRelated: It converts the surface-flux law into a local differential equation.