Conformal Field Theory, (2+1)-Dimensional Gravity, and the BTZ Black Hole

In three spacetime dimensions, general relativity becomes a topological field theory, whose dynamics can be largely described holographically by a two-dimensional conformal field theory at the ``boundary’’ of spacetime. I review what is known about this reduction–mainly within the context of pure (2+1)-dimensional gravity–and discuss its implications for our understanding of the statistical mechanics and quantum mechanics of black holes.