In the Active Groups report - what does "Activity Count" mean?

We're using "Activity Count" as an important metric to compare and assess general use of specific groups. However, people have asked me what counts as an "activity" in the "Activity Count" for the group list. The documentation on this report doesn't clarify what counts as an "activity" in the group. I'm assuming it includes all actions that are considered an interaction, plus content creation, plus content views for that group. Is this correct? Thanks for any clarity you can provide!