Hadrons
Hadrons are particles that are comprised of quarks and gluons. Baryons and mesons are different types of hadrons.
Protons and Neutrons are types of baryons. Examples of other baryons are Lambda particles and Omega particles. The reason for hadrons to to be consisted of 3 quarks, is that it takes 3 quarks of differing color charge to equal a net color charge of zero. Anti-baryons are 3 anti-quarks of the same type as the standard baryon counterpart.
Mesons are hadrons that are generally generated by weak interactions. They consist of a quark and an anti-quark of different flavors, held together by gluons. Pions and kaons are different types of meson.