Geofencing is when someone (whether it's you, a company, or something else) uses GPS to establish invisible, virtual boundaries. Then, depending on the service or app for which the geofence is set, you'll be able to—or even be unable to—access certain features.
Geofencing was invented in the early 1990s and patented in 1995 by American inventor Michael Dimino, using the first-of-its-kind GPS and GSM technology for a tracking system to locate objects anywhere on the globe from a remote location.