  This is the written version of a short talk given at the University of
Leipzig in December 1998. It reviews some general aspects of string theory from
the viewpoint of the search for an unifying theory. Here, special emphasis lies
on the motivation to consider string theory not only as the leading candidate
for the unification of gravity and the other fundamental forces of nature, but
also as a possible step towards a new understanding of nature and its
description within the framework of physical models. Without going into
details, some recent developments, including duality symmetries and the
appearance of $M$--theory, are reviewed.

High Energy Physics - Theory