Explorer

Explorer is a Fallout, Fallout 2, Fallout 3 and Fallout Tactics Perk.

Fallout, Fallout 2 and Fallout Tactics

 * Requirements: Level 9
 * Ranks: 1
 * Benefit: The mark of the Explorer is to search out new and interesting locations. With this Perk, you have a greater chance of finding special places and people in random encounters.

Fallout 3
(^NOTE:This does not add any locations to your Geomapping for Reilly Quest)
 * Requirements: Level 20
 * Ranks: 1
 * Benefit: When you choose the Explorer perk, every location in the world is revealed on your map.*^

(*NOTE: You cannot fast travel directly to the locations when you take this perk.)

Since there are many complete maps on the Internet, there is no reason to take this perk.Unless you want to explore by yourself, in-game.