Electromagnetics pertains to electromagnetic fields, electromagnetic waves, and various other electromagnetic constructs.

Light, microwaves, X-rays, cosmic radiation, etc. are all electromagnetic phenomenon.

In the case of static fields each component can exist independently meaning you can study magnetostatics and electrostatics separately.

In the case of time varying fields they are inseparably linked meaning electrodynamics also includes dynamic magnetic elements.

Should we define such a field by a vector representing the electric component, the magnetic component is perpendicular to it.

This is described by the differential equations:

${\displaystyle \nabla \times \mathbf {E} =-{\frac {\partial \mathbf {B} }{\partial t}}}$ (Faraday's law)

${\displaystyle \nabla \times \mathbf {B} =\mu _{0}\mathbf {J} +\mu _{0}\varepsilon _{0}{\frac {\partial \mathbf {E} }{\partial t}}}$ (Ampère-Maxwell law)

The divergence of the fields is described by the differential equations:

${\displaystyle \nabla \cdot \mathbf {E} ={\frac {\rho }{\varepsilon _{0}}}}$ (Gauss' law - electrostatics)

${\displaystyle \nabla \cdot \mathbf {B} =0}$ (Gauss' law - magnetostatics)