The code holds a geo link with latitude and longitude. iPhones open it in Apple Maps, Android in Google Maps, both with a pin on the spot and directions a tap away. It works for places that have no useful address: a car park entrance, a site gate, a pitch, a trailhead.
To find coordinates, long-press the spot in Google Maps or Apple Maps and copy the two numbers. Latitude comes first; in Ireland it is around 53, longitude is negative, around -8.
Questions
Should I use a Google Maps link instead?
A Google Maps link forces Google Maps and depends on Google keeping the format. A geo code opens whatever maps app the phone prefers and will still work in a decade.