Is there a term for maps you have to explore to reveal?
Solution 1:
This is going to vary wildly game by game, but the general concept you seem to be referring to is known as "Fog of War".
Wikipedia defines it as:
The term "fog of war" has become jargon in military and adventure video and computer games, in the more limited sense of enemy units or characters being hidden from the player. Often this is done by obscuring sections of the map already explored by the player with a grey fog whenever they do not have a unit in that area to report on what is there. The player can still view the terrain but not any enemy units on it.
When it applies to minimaps in particular (the entire Metroidvania genre springs to mind), I'm not sure if it has a precise analog, but Fog of War definitely describes the nature of the phenomenon, at least.
Solution 2:
In Age of Empires, this was referred to as the Fog of War (see Raven Dreamer's answer), and this is the most common name given to it. Age of Empires had two types of Fog of War (like most games that feature it) - one which would obscure enemy units and dim the map slightly, and one which was completely black. The completely black version is what you're referring to, and it is still called the Fog of War.
Games that feature it (to my knowledge) are mostly in the RTS genre, here are a few examples:
- Age of Empires series
- Command and Conquer series
- Warcraft series
- World of Warcraft (to an extent - world map has it but minimap doesn't, there are addons that reveal the world map before it has been explored too)
- Elder Scrolls series (not sure about Skyrim though, I've not played it yet)
- Baldur's Gate series
- Diablo series
- Most so-called "rogue-like" games
- Sid Meier's Civilization series
That's all I can think of right now, but there are literally hundreds more. Pretty much anything that's either RTS, TBS, RPG or Adventure. I don't think any list on SE would be comprehensive enough.
Solution 3:
I would call it Automaping.
Original text-based adventure games had no mapping at all; players were expected to make their owns maps with a pen and paper. (NORTH leads to the FIELDS, etc)
Some games added automapping, where the game would create a map for you in game keeping track of where you had been. It wouldn't generate a map for places you hadn't been yet.
Fog of war normally refers to the fact that once you have left an area, you aren't sure that nothing has changed. This is frequently shown in games with a light grey fog overlaid on the area to warn you that enemy units might be there.