We have now the possibility to see some analytics information for an existing Team through the new Analytics section available when click on the “Manage team” setting for that Team:
To access the Analytics section in a Team, just click on the Analytics Tab so you can see an overview of what has been happening there for the last 7 or 28 days:
As you can see, Analytics shows information about users’ activity in the Team, message posted in the Team or the active users vs. inactive users.
Reference