Board Admins can change the workflow for the board:
Note: the Backlog, Done and Trash columns are special: they can be hidden from view but they cannot be renamed, moved, or removed.
Check out this video on customizing workflows for boards.
Board Admins decide who is part of the board team:
Board Admins can permanently remove items from the board's Trash.
This simple mechanism provides a safety net for the entire team, by making deletion of cards a two-step process!
Usually, there is just one Board Admin: the person who created the board in the first place.
But it is possible for a board to have several Admins: anyone who is currently a Board Admin can upgrade any other Team Member or Visitor to the role of Board Admin. And, of course, so can the Account Owner.