This book covers some recent advances in string theory and extra dimensions. Intended mainly for advanced graduate students in theoretical physics, it presents a rare combination of formal and phenomenological topics, based on the annual lectures given at the School of the Theoretical Advanced Study Institute (2001) — a traditional event that brings together graduate students in high energy physics for an intensive course of advanced learning. The lecturers in the School are leaders in their fields.The first lecture, by E D'Hoker and D Freedman, is a systematic introduction to the...