Short answers, pulled from the story.
Quarks are fundamental constituents of matter that combine to form protons and neutrons. A proton consists of two up quarks and one down quark bound together by gluons, while neutrons contain one up quark and two down quarks. These particles are never found in isolation due to color confinement.
Murray Gell-Mann and George Zweig independently proposed the quark model in 1964. Deep inelastic scattering experiments at the Stanford Linear Accelerator Center provided the first concrete evidence for quarks in the late 1960s. The discovery of the charm quark in 1974, known as the November Revolution, finally convinced the physics community of the model's validity.
The universe contains six distinct types or flavors of quarks arranged into three generations. The first generation includes up and down quarks, the second generation includes strange and charm quarks, and the third generation includes top and bottom quarks. No evidence has been found for a fourth generation of quarks.
Color charge is a property of quarks that serves as the source of the strong interaction binding them together. This property is labeled as red, green, and blue, and the combination of these charges must always result in a color-neutral state. The theory describing this interaction is called quantum chromodynamics and involves the exchange of gluons.
Most of a hadron's mass comes from the gluons that bind the constituent quarks together rather than from the quarks themselves. A proton has a mass of approximately 938 MeV, of which the rest mass of its three valence quarks only contributes about 9 MeV. The remainder is attributed to the field energy of the gluons known as quantum chromodynamics binding energy.
Quark-gluon plasma is a theoretical phase of matter where quarks become deconfined and propagate as thermalized free excitations. This state is believed to have existed in the period prior to 10^-6 seconds after the Big Bang. Recent experiments at the Relativistic Heavy Ion Collider have yielded evidence for liquid-like quark matter exhibiting nearly perfect fluid motion.