These lecture notes provide a pedagogical introduction, with exercises, to the techniques used in attempts to construct vacua with stabilised moduli in string theory. The reader is only assumed to have a basic knowledge of general relativity, geometry and field theory. We emphasize physical arguments and focus on the latest developments involving the Swampland program that point to a tension for the existence of AdS vacua with small extra dimensions or dS vacua with parametric control. We include a brief summary of the current status of these thorny issues. Unlike many other reviews we make almost no use of the technicalities associated to supersymmetric geometries. These notes are largely based on lectures given at the CERN Winter School on Supergravity, Strings and Gauge Theory and in the Tehran School on Swampland Program held in the summer of 2022.

93 pages, 11 figures; v2: references added