The idea is that everyone downloads the same starting save file, and then plays the game. You can compare strategies and outcomes - and its relevant to compare, because the map is the same. We have "spoiler" threads, where the strategies are discussed, and over time, we rank people on a leaderboard. We have a variety of difficulty levels and try to play all the different civilizations.
Primarily its about fun, and about learning off each other to improve the game.
Main webiste for it is gotm.civfanatics.net