  This paper provides an introduction to equivariant cohomology and homology
using the approach of Goresky, Kottwitz, and MacPherson. When a group G acts
suitably on a variety X, the equivariant cohomology of X can be computed using
the combinatorial data of a skeleton of G-orbits on X. We give both a geometric
definition and the traditional definition of equivariant cohomology. We include
a discussion of the moment map and an algorithm for finding a set of generators
for the equivariant cohomology of X. Many examples and explicit calculations
are provided.
