Wikipedia provides a reasonable introduction.
The Standard Model of particle physics is a theory which describes three of the four known fundamental interactions between the elementary particles that make up all matter. It is a quantum field theory developed between 1970 and 1973 which is consistent with both quantum mechanics and special relativity. To date, almost all experimental tests of the three forces described by the Standard Model have agreed with its predictions. However, the Standard Model falls short of being a complete theory of fundamental interactions, primarily because of its lack of inclusion of gravity, the fourth known fundamental interaction, but also because of the large number of numerical parameters (such as masses and coupling constants) that must be put "by hand" into the theory (rather than being derived from first principles).
http://en.wikipedia.org/wiki/Standard_ModelOne is perhaps familiar with particles of matter, which are described by the Standard Model as having an intrinsic property known as 'spin' whose value is determined to be 1/2.
Spin - "is the angular momentum intrinsic to a body, as opposed to orbital angular momentum, which is the motion of its center of mass about an external point."
http://en.wikipedia.org/wiki/Spin_%28physics%29http://en.wikipedia.org/wiki/Spin-statistics_theoremForces in physics are the ways that particles interact and influence each other. . . . The standard model explains such forces as resulting from matter particles exchanging other particles, known as force-mediating particles.
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