2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/49903In these lectures we review the basic ideas of perturbative and non-perturbative string theory. On the non-perturbative side we give an introduction to D-branes and string duality. The elementary concepts of non-BPS branes and noncommutative gauge theories are also discussed.37+1 pages, LaTeX file, no figuresHigh Energy Physics - TheoryGeneral Relativity and Quantum Cosmologytext