The gravity-gauge theory correspondence

At the end of 1997 a young Argentinian physicist conjectured that certain s tring theories are identical to certain other well-understood theories call ed gauge theories. This conjecture has been at the focus of attention of mu ch of the string theory community over the last year and a half, and has ge nerated over 1000 research papers. In this article I will attempt to explai n the conjecture and why it has generated so much excitement.