Doubles... triples... etc

I just want to know all the differences between a doubles game (or triples or quadruples) and a regular game. Obviously, there are teams, but what specifically changes about the game play? I was playing a doubles game, and I see someone has 5 people on a territory before they have even played?!?!
Some questions:
1. What if you and your ally/allies collectively hold a continent?
2. Do your allies benefit from you holding a continent?
3. If you lose and your ally wins the game, do you still get points?
Some questions:
1. What if you and your ally/allies collectively hold a continent?
2. Do your allies benefit from you holding a continent?
3. If you lose and your ally wins the game, do you still get points?