The Enigma grid map was used on German U-boats for position messages, sent over to the German U-boat command. It showed several named grids, which defined certain areas. Big squares, named with 3 letters were split down to smaller grids and named with numbers from 1-99. A radio message with coordinate AM32 let the U-boat commander know he was to gravel to grid AM32 where a convoy was sighted. To know where AM32 was, he had to consult this map.
There were a lot of different issues of this map. The most used and the most famous, the 3401, showed the Northern Atlantic area.
Excellent links on the Enigma Machine ...
Bletchley Park Exhibition
The German Inigma Cipher Machine
The Rutherford Journal
Enigma Machine Captured