Bosons are particles that follow Bose-Einstein statistics. This means that there are no restrictions how many of them can occupy the same quantum state. Other class of particles are fermions, two of which can’t occupy the same quantum space if they are identical.
All matter is made of elementary particles quarks and leptons, which are fermions, whereas elementary bosons are force carriers. Unlike fermions that have half-integer spin, bosons have integer spin (0, 1, 2, etc.).
Elementary bosons are gluon, W and Z bosons, photon and theorized graviton, all of them force carriers of strong force, weak force, electromagnetism and gravity, respectively. Another elementary boson is the Higgs boson, confirmed in 2013 after an experiment in the Large Hadron Collider. Higgs boson is the only scalar boson, which means it has no spin.
Composite bosons are all those non-elementary particles that have integer spin as a result of their constituents’ spins added. Meson is one example, since it’s made of a quark and an antiquark and can have spin of 0 or 1, depending on type of quarks that make the meson. Other examples are nuclei with even mass number like helium-4 atom with two protons, two neutrons and two electrons.
Bosons were named after Satyendra Nath Bose by Paul Dirac, for Bose’s contribution in Bose-Einstein statistics that theorizes the characteristics of elementary particles.