Indoor location is a topic that has attracted lot attention in the past two decades. This is mainly due to the success of outdoor location, typically GPS, and the provided services based on this technology. The goal of indoor location is to provide similar services that can be found in outdoor location where GPS signal can not penetrate (buildings such as airports, malls, museums and homes). This tutorial presents the different technologies available for indoor location, the algorithms used, example applications and future research lines. Special attention will be devoted to location systems based on Wi-Fi fingerprinting.