2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/55178After briefly reviewing basic concepts of perturbative string theory, we explain in simple terms some of the new findings that created excitement among the string physicists. These developments include non-perturbative dualities and a unified picture that embraces the so-far known theories. (An overview for non-experts)16 p, latex, lprocl.sty, 12 figs, Contribution to the Proceedings of Lepton-Photon 97. Continuous updates at http://nxth21.cern.ch/~lerche/papers/strings.ps.gzHigh Energy Physics - TheoryHigh Energy Physics - Phenomenologytext