Select if you want to follow/unfollow changes on behalf of your teams(s), i.e. marking this item as being of particular interest to a team you are part of.
Marking as followed will ensure that all the team members will see changes, including comments, in their personal activity feed and in the item will be shown in the the specific Follow Lists in the Dashboard. Ummarking i.e. unfollowing will do the vice versa.
Read more about following items here.