Maxwell's equations are the fundamental laws governing electromagnetism. They describe how electric and magnetic fields are generated and interact. The key equations are:
$$ \nabla \cdot \mathbf{E} = \frac{\rho}{\varepsilon_0} $$
(Gauss's Law for Electricity)
$$ \nabla \cdot \mathbf{B} = 0 $$
(Gauss's Law for Magnetism)
$$ \nabla \times \mathbf{E} = -\frac{\partial \mathbf{B}}{\partial t} $$
(Faraday's Law)
$$ \nabla \times \mathbf{B} = \mu_0 \mathbf{J} + \mu_0 \varepsilon_0 \frac{\partial \mathbf{E}}{\partial t} $$
(Ampère-Maxwell Law)