No,what the hell is that? Did they put something in my brain? It couldn't have been anything large.
I'll give you an example.
Lets say you own a small clothing store and you have a small budget for advertising. You can pay to geofence malls, or competitors who draw lots of traffic. A "fence" based on location coordinates is set up around those locations (as many as you want) and anyone who walks through the wall/fence is captured.
Once captured if that person opens any of several thousand apps on their smartphone they can see a little banner ad for your store which they can click to call or to go to your site or to a page with more info.
One of the local high end outdoor mall/lifestyle areas here geofences the wealthy areas of Naples and Bonita all the time. Very effective.