“The electric and magnetic fields described in Maxwell’s equations are quantized, and photons appear as excitations of those quantized fields. In QED, photons serve as carriers of electric and magnetic forces. For example, two identical charged particles electrically repel one another because they are exchanging what are called virtual photons.
Though the mathematical complexities of QED are formidable, it is a highly successful theory that has now withstood decades of precise experimental tests.”
Electroweak Theory (EWT)
The Electroweak Theory governs the Weak Interaction as well as the Electromagnetic Interaction. The Exchange Particles of the Weak Interaction are the W+, W– and Z Bosons
The existence of the exchange particles, the neutral Z particles and the charged W particles, was verified experimentally in 1983 in high-energy proton-antiproton collisions at CERN.
The theory was developed independently in 1960s by Sheldon Lee Glashow, Abdus Salam, and Steven Weinberg
Quantum Chromodynamics (QCD)
QCD governs the Strong Interaction, which takes place by exchanging Gluons.
The Strong Interaction acts only on particles with color-charge, that is, quarks and particles built from quarks, such as protons and neutrons.
The color-charges (red, green, and blue) are comparable to positive and negative electric charge: particles with opposite colors attract and particles with the same colors repel.
The theory was developed in 1973 by Harald Fritzsch, Heinrich Leutwyler, and Murray Gell-Mann.