Character and Player Knowledge

When roleplaying, there is significant difference between the knowledge of a player and the character they are playing. The player presumably knows how to read, how to do math, has an understanding of planets and stars, that lightning is just a natural occurance and that the game world is a made up place that follows certain rules, whereas their character may have no idea about any of this. A player also remembers events, places and NPCs from previous adventures with different characters.

On the other hand, a character may know more about the history and workings of the game world than their player does. After all, the character has spent all their life in this world. If any knowledge is part of a character's background or just common knowledge within the game setting, the GM may just tell the group about it when it comes up.

However, if some piece of information is relatively obscure or only known by few people, succeeding on a roll for a knowledge ability or nature is required for the character to know about it. Remembering some arcane knowledge the character has heard about may even take some time.