Wikipedia Excerpt: The Universal Transverse Mercator (UTM) projected coordinate system uses a 2-dimensional Cartesian coordinate system to give locations on the surface of the Earth. It is a horizontal position representation, i.e. it is used to identify locations on the Earth independently of vertical position, but differs from the traditional method of latitude and longitude in several respects. (more information)
In the OTP22 ARG, UTM coordinates are commonly used to identify locations of Dead drops. These coordinates are commonly in a form similar to 10/324234/654654 (region/northing/easting) and can be translated into regular longitudes and latitudes for our purposes.