The charm quark or c quark (from its symbol, c) is the third most massive of all quarks, a type of elementary particle. Charm quarks are found in hadrons, which are subatomic particles made of quarks. Example of hadrons containing charm quarks include the J/ψ meson (J/ψ), D mesons (D), charmed Sigma baryons (Σ
c), and other charmed particles.
It, along with the strange quark is part of the second generation of matter, and has an electric charge of +2⁄3 e and a bare mass of 1.29+0.05−0.11 GeV/c2. Like all quarks, the charm quark is an elementary fermion with spin-1⁄2, and experiences all four fundamental interactions: gravitation, electromagnetism, weak interactions, and strong interactions. The antiparticle of the charm quark is the charm antiquark (sometimes called anticharm quark or simply anticharm), which differs from it only in that some of its properties have equal magnitude but opposite sign.
The 1974 discovery of the J/ψ (and thus the charm quark) ushered in a series of breakthroughs which are collectively known as the November Revolution.
(Source: Wikipedia—Charm Quark, The Charm of Strange Quarks—Mysteries and Revolutions of Particle Physics)