A gluon is a fundamental particle in the field of particle physics. It acts as the exchange particle for the strong force, which is one of the four fundamental forces in nature. Gluons are responsible for holding quarks together to form protons and neutrons, the building blocks of atomic nuclei. Gluons are massless and carry the "color charge," a property related to the strong force. They interact with quarks and other gluons, creating a complex web of forces that keeps atomic nuclei stable. This interaction is essential for the existence of matter as we know it, influencing the behavior of particles like protons and neutrons.