What is the meaning of Standard Model ?

                                    The Standard Model of particle physics is a theory concerning the electromagnetic, weak, and strong nuclear interactions, which mediate the dynamics of the known subatomic particles. Developed throughout the mid to late 20th century, the Standard Model is truly “a tapestry woven by many hands”, sometimes driven forward by new experimental discoveries, sometimes by theoretical advances. It was a collaborative effort in the largest sense, spanning continents and decades. The current formulation was finalized in the mid-1970s upon experimental confirmation of the existence of quarks. Since then, discoveries of the bottom quark (1977), the top quark(1995), and the tau neutrino (2000) have given further credence to the Standard Model. More recently (2011–2012), the possible detection of the Higgs boson would complete the set of predicted particles upon its verification. Because of its success in explaining a wide variety of experimental results, the Standard Model is sometimes regarded as a "theory of almost everything".

More specifically, it makes verifiable predictions for the nature of causality in the quantum realm, thus illuminating a wider philosophical problem. The Standard Model falls short of being a complete theory of fundamental interactions because it makes certain simplifying assumptions. It does not incorporate the full theory of gravitation as described by general relativity, or predict the accelerating expansion of the universe (as possibly described by dark energy). The theory does not contain any viable dark matter particle that possesses all of the required properties deduced from observational cosmology. It also does not correctly account for neutrino oscillations (and their non-zero masses). Although the Standard Model is believed to be theoretically self-consistent, it has several apparently unnatural properties giving rise to puzzles like the strong CP problem and the hierarchy problem. Also, the treatment of larger numbers of particles is the realm of statistical physics. Moreover, when studied in the context of an extremely small scale, quantum mechanics starts to kick in, and give rise to several phenomena such as the particle in a box problem^[3][4] and wave–particle duality, or theoretical considerations, such as whether particles can be considered distinct or identical.

Nevertheless, the Standard Model is important to theoretical and experimental particle physicists alike. For theorists, the Standard Model is a paradigm of a quantum field theory, which exhibits a wide range of physics including spontaneous symmetry breaking, anomalies, non-perturbative behavior, etc. It is used as a basis for building more exotic models that incorporate hypothetical particles, extra dimensions, and elaborate symmetries (such as supersymmetry) in an attempt to explain experimental results at variance with the Standard Model, such as the existence of dark matter and neutrino oscillations. In turn, experimenters have incorporated the Standard Model into simulators to help search for new physics beyond the Standard Model.