A model of the basic particles and forces featuring six quarks, three charged leptons, three massless neutral leptons and four fundamental force carrying bosons. The twelve fermions are arranged into three generations, while the bosons serve to explain the electromagnetic interaction plus the strong and weak nuclear forces (and the Higgs mechanicsm). Do NOT use this tag for the standard model of cosmology, etc..
The Theories of the Standard Model
The theories combined by the standard model are:
- quantum-chromodynamics of the strong interaction.
- electroweak-theory of the electromagnetic (Note that electromagnetic alone is described by quantum-electrodynamics and weak interactions. This is along with an additional higgs-mechanism to explain the Electroweak symmetry breaking (why do the W & Z bosons have mass?)
The Standard Model, describes all experimentally known fundamental interactions (bosonic fields) and fermionic fields, except for gravity, which is classically described by general-relativity.
One of the major needs for theories like string-theory is precisely this shortcoming of the standard model. Other needs include the vastly large number of dimensionless constants, the need for renormalisation, etc.