Bosons are what we call force "carriers". When any reaction takes place or any force is applied, it is done so by exchanging Bosons. This is a physically difficult thing to visualize and understand. The following link is intended to help describe this exchange.
The bosons that have been observed experimentally are the photon, the gluon, the W+, W-, and the Z. The Higgs boson and graviton have yet to be observed experimentally. These particles are how quarks, leptons, and composites of them interact. This is to say that particles interact by exchanging force carrier particles. Important to note that a particle can only be affected by a particular force if that particle can emit or absorb that type of force carrier. For example protons and electrons can interact by the exchange (absorption or emission) of photons. Each of the four fundamental forces can be attributed to one or more of the bosons. Table 1 shows the breakdown of which force carrier corresponds to which force. A very interesting result is the W Bosons are the only Bosons that can change the flavours of quarks by absorption or emission.
| Interaction Field | Boson | Spin Quantum Number |
|---|---|---|
| Weak | W+, W-, Z | 1 |
| Strong | Gluons | 1 |
| Electromagnetic | Photons | 1 |
| Gravitational | Gravitons (hypothesized) | 1 |
| Higgs | Higgs (hypothesized) | 1 |