Latitude and longitude
Latitude ranges from -90 to 90 degrees and describes north-south position. Longitude ranges from -180 to 180 degrees and describes east-west position. Many consumer maps display coordinates in latitude, longitude order.
WGS84
WGS84 is the global reference system used by GPS and many online maps. A coordinate is more meaningful when you also know the datum or reference system behind it.
Decimal, DMS and DDM
Decimal degrees are compact and easy to paste into web maps. DMS uses degrees, minutes and seconds. DDM uses degrees and decimal minutes. All three can describe the same physical point.
UTM
UTM divides the world into longitudinal zones and represents positions with easting and northing values in meters. The zone and hemisphere are essential parts of a complete UTM coordinate.