Gluons are elementary particles that acts as the exchange particles (or gauge bosons) for the strong force between quarks. It's analogous to the exchange of photons in the electromagnetic force between two charged particles.   They "glue" quarks together, forming protons and neutrons.


In Feynman diagrams, emitted gluons are represented as helices. This diagram depicts the annihilation of an electron and positron. image: wikipedia

In technical terms, gluons are vector gauge bosons that mediate strong interactions of quarks in quantum chromodynamics (QCD). 

Gluons themselves carry the color charge of the strong interaction. This is unlike the photon, which mediates the electromagnetic interaction but lacks an electric charge. Gluons participate in the strong interaction in addition to mediating it, making QCD significantly harder to analyze than QED (quantum electrodynamics), mostly due to much higher energies involved.

Fields due to color charges, as in quarks (G is the gluon field strength tensor). These are "colorless" combinations. Top: Color charge has "ternary neutral states" as well as binary neutrality (analogous to electric charge). Bottom: Quark/antiquark combinations. image: wikipedia/Maschen 

 Quarks carry three types of color charge; antiquarks carry three types of anticolor. Gluons may be thought of as carrying both color and anticolor. This gives nine possible combinations of color and anticolor in gluons.

Adapted from : Gluon. (2018, January 15). In Wikipedia, The Free Encyclopedia. Retrieved 09:39, February 10, 2018, from