The socalled "displacement current" is a misnomer. It's not a current but it's simply part of one of Maxwell's equations, the Ampere-Maxwell Law, which reads in Heaviside-Lorentz units
$$\vec{\nabla} \times \vec{B}-\frac{1}{c} \partial_t \vec{E}=\frac{1}{c} \vec{j}.$$
This is the "microscopic form" of the law, and ##\vec{j}## is the total current density.
The source of the electromagnetic field are charge and current densities.