When two civilizations are in the same team in Civilization V, they share research and diplomacy apart from City State alliances, but have separate social policies, separate treasuries, separate tourism, etc.
Overall it seems that teamed players are considered separate civilizations in some matters and the same civilization in others. What are the complete effects of being in the same team?
There's a GameFaqs thread discussing this, here is a list one of the users there compiled:
When any player on the team researches the tech tree all of the teammates get the technology. If you both research the same tech at the same time, the time for completing it will be halved.
You also see the map under fog of war which is cleared by the other player on the team.
If any player on the team declares war on someone, the whole team goes into the war.
Also, the the points of everyone in the team will be counted together and it shows a team score at the list on the right.
You can gift units (both combat & civilian) to your teammates just like you can for city-states normally.
However you won't automatically share luxory- & strategic resources, but the standard trading mechanics work as normal so you can trade half of what you have over to your teammate for example.
You have permanent Declaration of Friendship with each other
You'll still feel ideological pressure (reduced happiness for adopting different ideologies) from team mates
Autocracy tenet Futurism doesn't work against team mates.
As he mentions himself, there is probably more.
