Minecraft wiki entry for Explorer_Map, associated text: A ocean explorer map in the off-hand, an woodland explorer map in the main hand, and a cartographer villager in between them.
A partially-explored explorer map.
Two fully-explored maps of the same place, one of which is a woodland explorer map.
A player holding a buried treasure explorer map. The player can see the red X on the right side of the map.
Purchasing explorer maps from a cartographer.