Quantum electrodynamics

Abelian gauge theory describing quantum interactions of the electromagnetic field with matter

Quantum electrodynamics (also called QED for short) is the quantum theory of electricity and magnetism. QED describes how electric and magnetic forces work on the scale of things smaller than atoms. QED also describes how single photons of light behave. QED is one of the most well-tested theories in physics.

Feynman diagram elements. "B" is where one photon ends up, at a certain time. "D" is where one electron ends up at a certain time. "E" is the point where one electron and one photon meets; that photon gets absorbed by that electron
In this Feynman diagram, an electron and positron destroy each other, producing a virtual photon which becomes a quark-antiquark pair. Then one radiates a gluon