Confused Scout

Hello, I'm debating whether or not I should buy a GPS device to go Geocaching and noticed my phone actually had a built in GPS. However, the last time I tried to use it alongside the Geocaching app, the app failed because I wasn't connected to Wifi. I'm not sure whether or not I need a separate mapping app connected to the phone's GPS chip (my phone is a Android Moto G) to do this, or if I'm not understanding something about the app. If anyone could provide some information on this, I would greatly appreciate it.