Exposure is defined as “the situation of people, infrastructure, housing, production capacities and other tangible human assets located in hazard-prone areas” (UNDRR 2017). Exposure models in this chapter are mostly focused on the identification of population, buildings, and critical infrastructure at risk. Conceptually, exposure is a necessary, but not sufficient, determinant of risk, since it is possible to be exposed but not vulnerable to a hazard (as for instance, by living in a floodplain but having sufficient means to modify the asset’s characteristics to avoid or mitigate future potential losses, or by occupying a building in an earthquake prone region that was designed and built according to earthquake-resistant provisions). Within a risk assessment, this means that an exposure model is always required for estimating the losses on population and/or exposed assets.