2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/55914This is a write-up of lectures given at the 1998 Spring School at the Abdus Salam ICTP. We give a conceptual introduction to D-geometry, the study of geometry as seen by D-branes in string theory, and to noncommutative geometry as it has appeared in D-brane and Matrix theory physics.LaTeX, 26 pp. Added referenceHigh Energy Physics - Theorytext