We briefly introduce black holes in the theory of general relativity and
study their thermodynamic properties. We then move to supersymmetric
black holes, which are solutions to superstring theories. As an example
we concentrate on the D1-D5 brane system in five dimensions, in the
context of compactifications of type IIB superstring theory on a
5-torus. We compute the macroscopic (Bekenstein-Hawking) entropy of the
corresponding black hole. We then give a microscopic interpretation of
this result in terms of string microstates, following the work of
Strominger and Vafa. We end by mentioning some current open problems in
black hole physics. |