The Standard Model of particle physics is a well-established theoretical framework that describes three of the four known fundamental forces in the universe: electromagnetic, weak, and strong forces. It does not incorporate the fourth fundamental force, gravity, which is described by General Relativity.
In the Standard Model, the fundamental constituents of matter are divided into two groups: fermions and bosons.
Fermions
Fermions are the building blocks of matter and come in two types: quarks and leptons. Quarks make up protons and neutrons, which are found in the nucleus of atoms. Leptons include electrons (which orbit the nucleus of atoms) and neutrinos (extremely light particles that rarely interact with other matter). Each of these comes in six different varieties or “flavors.”
Bosons
Bosons, on the other hand, are particles that carry forces. The photon carries the electromagnetic force, W and Z bosons carry the weak force, and gluons carry the strong force. The Higgs boson, discovered in 2012 at the Large Hadron Collider, is associated with the Higgs field, a universal field thought to give particles their mass.
Despite its success at explaining the behavior of particles and forces at the quantum level, the Standard Model has limitations. For instance, it does not incorporate the force of gravity, nor does it explain the nature of dark matter or dark energy, mysterious substances that make up about 95% of the universe. Furthermore, it does not explain why there is more matter than antimatter in the universe.
Scientists continue to search for a more comprehensive theory (often referred to as a “Theory of Everything”) that would reconcile the Standard Model with General Relativity and provide a full description of all known fundamental forces and particles.