Quantum Electrodynamics (QED) is a fundamental theory in physics that describes how light and matter interact. It combines the principles of quantum mechanics and the theory of electromagnetism, focusing on the behavior of photons (light particles) and charged particles like electrons. QED explains phenomena such as the emission and absorption of light by atoms. In QED, particles interact through the exchange of virtual particles, which are temporary fluctuations that occur during interactions. This framework has been crucial for understanding various physical processes, including the fine structure of atomic spectra and the behavior of particles in strong electromagnetic fields.