Latitude and longitude
The two numbers that place any point on Earth.
Latitude measures north and south of the equator (from -90 to 90), longitude east and west of Greenwich (from -180 to 180). Together they place a point: London's centre is about 51.51, -0.13. Four decimal places are about 10 metres.
Spreadsheets you upload to xMap Flows are read for columns named lat and lng, latitude and longitude, or one "lat, lng" column; decimal commas are understood.