The gluon is the gauge boson of the strong interaction in quantum chromodynamics.
Gluons transmit the strong force between quarks and carry the force’s associated color charge. This makes them different from photons, which carry the electromagnetic interaction but have no electric charge. Because gluons themselves carry color charge, they can interact with one another, producing the distinctive behavior of the strong force.
Quantum chromodynamics, or QCD, describes quarks and gluons. At very high energies or short distances, quarks interact more weakly, a property called asymptotic freedom. At ordinary distances, the strong interaction becomes powerful and quarks are confined inside composite particles such as protons and neutrons.
The gluon was not observed as an isolated particle. Evidence for gluons came from three-jet events in electron–positron collisions, first observed at the PETRA accelerator in 1979. The name reflects the particle’s role in binding quarks together, although the full theory also depends on the non-Abelian structure of QCD.