Google latitude longitude is actually a point on a map (Google map, for instance). The Google latitude longitude components in Google map constitute a point so that a GPS tracker like Garmin StreetPilot 7200 can pinpoint you exact location in real-time.
A sample Google map where the latitude and longitude coordinates are set is shown below. In GPS devices, the photo is very much similar. (Click on Image to enlarge)
The photo shown above is Google map. In setting it up, all you have to do as a user is set the Google latitude and longitude coordinates and you can view the entity (person, place, activity depending on your device and settings) at that exact location.