String theory and gravitation. Towards quantum geometry

This is an abbreviated written version of pedagogical lectures delivered in the workshop 'Noncommutative Differential Geometry and its Application to Physics' (Shonan, May 31-June 4, 1999). The purpose was to give an overview on the nature of string theory as quantum gravity. After giving a brief historical introduction, we discuss how general relativity can be derived as consistent local field theory of massless spin 2 particle in the low-energy limit. Then, several important issues, such as the manner how string theory contains gravity, the stringy resolution of ultraviolet difficulty, duality between open and closed strings, are critically reviewed. (author)