Let's see if I can answer this before one of the nice Admins moves the thread to Feedback...
Teams are divided into three leagues according to how many members they have - Small, Medium, Large.
There are several games that get points for your team. The two games designed especially for teams are Team v Team (usually called TvT) and Team Heroes. In each case scores are averaged and it's the average which counts for the team as a whole - in Heroes this is a defined number (X) based on the team size and only the top X players count whereas in the TvT a minimum of six players must record a score and everyone's score, as long as it's above 300, counts in the average.
Then there's a group of other games which carry team points for the top 200 players scoring on any given day in each league. Those games are: Easy, Average (Something for Everyone), Who's the Smartest, New Questions, World, Daily, Pot of Gold, Who Am I?, and Mind Melt. As you will see, some of those games are open to everyone and some are for Gold Members only.
The scoring is described more fully here
Hope this helps.