Graybeard
Explorer
I've played in very detailed world games and some that only the basic details were done before the games started. Both can be fun depending on the players and what they are told beforehand. My game is a little of both. I made a map of the continent and starting kingdom\country, made a list of well known people in that country, and then let the players do the rest. As they explore and meet new NPCs, I add to the campaign world. The players all made good backgrounds for their characters and included basic historical notes for the area they were from. I included those in the campaign world and have expanded upon them. Two players even made maps of their hometowns and neighborhoods.