Short answers, pulled from the story.
A hadron is a composite subatomic particle made of two or more quarks held together by the strong nuclear force. They are analogous to molecules, which are held together by the electric force. The proton and the neutron are the most familiar examples.
Baryons are hadrons containing an odd number of valence quarks, usually three, while mesons contain an even number, usually a quark and an antiquark. Baryons are fermions with half-integer spin and a baryon number of one, and mesons are bosons with integer spin and a baryon number of zero. Protons and neutrons are baryons, while pions and kaons are mesons.
Most of the mass of a hadron comes from the binding energy of the strong interaction, not from its valence quarks. Because of mass-energy equivalence, the energy of the strong force that holds the quarks together accounts for most of the particle's mass.
Almost all free hadrons and antihadrons are believed to be unstable and eventually decay into other particles. The only known possible exception is the free proton, which appears stable or takes on the order of ten to the thirty-fourth years or more to decay. The free neutron is the longest-lived unstable hadron, with a half-life of about 611 seconds and a mean lifetime of 879 seconds.
The term hadron was introduced by L. B. Okun in a plenary talk at the 1962 International Conference on High Energy Physics at CERN. The word is derived from Greek and signifies large or massive, in contrast to a term meaning small or light.
Tetraquarks and pentaquarks are exotic hadrons. The tetraquark Z(4430) was discovered in 2007 by the Belle Collaboration and confirmed as a resonance in 2014 by the LHCb collaboration. Two pentaquarks, P(4380) and P(4450), were discovered in 2015 by the LHCb collaboration.
Color confinement is the rule that a hadron must have zero total color charge, meaning it must be colorless or white. This is achieved either by a quark and an antiquark of the matching anticolor, forming a meson, or by three quarks of different colors, forming a baryon.