In particle physics, bosons are subatomic particles that obey Boseâ€“Einstein statistics. Several bosons can occupy the same quantum state. The word boson derives from the name of Satyendra Nath Bose.
Since bosons with the same energy can occupy the same place in space, bosons are often force carrier particles. In contrast, fermions are usually associated with matter (although in quantum physics the distinction between the two concepts is not clear cut).
Bosons may be either elementary, like photons, or composite, like mesons. Some composite bosons do not satisfy the criteria for Boseâ€“Einstein statistics and are not truly bosons (e.g. helium-4 atoms); a more accurate term for such composite particles would be "bosonic-composites". (Wikipedia)