A boson is a particle which behaves usually as a force-carrier. Each of the four fundamental forces (Strong Nuclear, Weak Nuclear, Electromagnetic, and Gravity) has one or more bosons (called gauge bosons) that transmit the respective forces. These gauge bosons are the quanta of the forces. Bosons, which have an integer spin, can occupy the same space unlike matter (feminons) which cannot. The Higgs Boson
which is being searched for by the Large Hadron Collider
is also a boson which gives particles mass; it does not belong with the four fundamental forces but is still a boson (it has an integer spin).