It is a function addressed to projects that are managed in group (for instance, by a charity, community, sport teams, music band, etc.).
With the Team function you can invite other people to join your project as a team, so they can share it, post updates, etc. The organizer of the project can check all the activities that other team members did on the project, like shares and collected support.
This function is recommendable to projects that needs to be managed by more than 1 person, to being able to achieve a better result.
If you are interested to use the Team function, go to [My project] page and select the option to run your project as a team.