2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/821I present a somewhat selective review of microlensing theory, covering five major areas: 1) the derivation of the basic formulae, 2) the relation between the observables and the fundamental physical parameters, 3) binaries, 4) astrometric microlensing, and 5) femtolensing.14 pages, 3 figures. To be published in "Microlensing 2000, A New Era of Microlensing Astrophysics", eds., J.W. Menzies and P.D. Sackett, ASP Conference SeriesAstrophysicstext