The quantum theory of the electromagnetic interaction and the properties and behavior of electrons, positrons, photons, and the electromagnetic field.
A theory that applies the principles of the quantum theory to electrodynamics: it describes how photons interact electromagnetically with electrons, protons, etc.
A quantum field theory of electromagnetism that explains the interactions between electrically charged particles and photons. According to quantum electrodynamics, charged particles interact with one other by emitting or absorbing photons, which are the carriers of the electromagnetic force. Quantum electrodynamics correctly predicts such phenomena as the structure of atoms, and the creation and annihilation of particles (for example, when matter and antimatter collide). Quantum electrodynamics is one of the most well-tested, accurate, and successful theories in physics.