The Exploration Region was the area of the galaxy on which the explorer Reidi Artom chose to focus her scouting career. She was responsible for renewed interest in eight systems in the region, including the Cularin system.
Behind the scenes
The Exploration Region was most likely a typo for the Expansion Region, as elsewhere in the same source, Cularin is said to be in the Expansion Region. It is possible, however, that the Exploration Region was a smaller subsection of the Expansion Region (maybe including some of the Mid Rim as well) which had not been surveyed thoroughly.