Can I send maps to other players?
Yes, if the other players in the game do not have the map that you've selected, it will be transferred to them when they enter the chatroom. A number will appear to the left of their name-- this is the % of the map that has been copied over. You cannot start the game until every player has the map.

What are my diplomatic options?
Clicking on the Diplomacy button during a multiplayer game brings up the Diplomacy Menu. From here, you can choose to Ally or Share Vision with other players in the game. Allied units will not attack each other, although area-affect attacks can still damage friendly units. Free For All, One on One, and Ladder games do not allow allies or shared vision.

Just what is "Team" play?
Team games add a whole new level to cooperative play. Set before the game starts, a Team is effectively one side controlled by two or more players. Resources, technologies, and vision are all shared by the Team members, who don't have to play the same species. Unit control is also shared-- units that are currently selected by your teammates are marked so that you won't accidentally override your teammate's orders.