There is broad class of particle physics candidates for the dark matter that are referred to as Weakly Interacting Massive Particles or WIMPs. This class includes several proposed particles (massive Dirac neutrinos, cosmions, SUSY relics) that have masses of order a few GeV to a few hundred GeV and interact through the exchange of W's, Z's, higgs bosons and other intermediaries. In this talk, I will give a brief introduction to WIMPs. I refer interested readers to recent, more detailed reviews [61,50,37].
The early universe is a wonderful particle accelerator. WIMPs could be produced through reactions such as , where X denotes the WIMP particle. WIMPs, of course, can be annihilated through the backreaction, . As long as , the WIMP number density would be comparable to the number density of electrons, positrons, and photons. However, once the temperature drops below , the WIMP abundance begins to drop. It will fall until the WIMP number density is so low that the WIMP mean free time for annihilation exceeds the age of the universe. This ``freeze-out'' occurs at a density determined by the WIMP annihilation cross-section and implies that
The first proposed WIMP candidates were heavy fourth generation neutrinos [36,41]. If the neutrino mass was of order 2 GeV, then its relic abundance would be sufficient for . Experimental dark matter searches  ruled out these particles as dark matter candidates.
Supersymmetry is an elegant extension of the standard model of particle physics. It is the only so-far ``unused'' symmetry of the Poincare group and has the virtue of protecting the weak scale against radiative corrections from GUT and Planck scale. Local supersymmetry appears to be an attractive route towards unifying all four forces and is a basic ingredient in superstring theory. Supersymmetry transforms bosons into fermions (and vice-versa). As supersymmetry has a new symmetry, R parity, it can imply the existence of a new stable particle. In much of the parameter space of the minimal supersymmetric model, this new stable particle (which we will refer to as the``neutralino'') has predicted properties such that it would comprise much of the density of the universe .