http://www.2kgames.com/civ4/pitboss.htm
Hot damn. Who's ready for some epic Civ4 game action?
While running, players will be able to log in and continue their progress in a game at any time. Once satisfied, players are welcome to log out and continue later.
Once you are in the game, however, Civilization IV may play a bit differently from classic multiplayer games. If all participants are currently logged into the game, it will play exactly the same as a classic Civilization IV multiplayer game. You are free to move as soon as it is your turn, you are free to chat to the other players, you are free to conquer the world! However, the most important difference when playing a PitBoss game is that all other participants may not always be logged in.
If you are engaged in a PitBoss game, and another player logs out, you are free to make your move if it is your turn. Afterwards, the game is on hold until that player logs back in and makes his move. You are free to study the map. You can even manage cities and change technologies. But you cannot move your units until all other players finish their turns, and your turn is again active.
If the PitBoss has been set up to do so, you are free to register for alert E-mails that you will receive when your turn is made available. This is accomplished by entering your E-mail address in the player details screen (Alt-D). Also, the PitBoss may be set up to run a turn timer. You may have a limited time (typically 24 hours or so) to make your move. Make sure you recognize when a timer is being used since not moving within this time will result in passing on your turn!
Hot damn. Who's ready for some epic Civ4 game action?