From the "About This Group" link:
http://www.democraticunderground.com/?com=about&forum=1263
Group Hosts have the following abilities in their assigned groups:
Lock thread (Reason: Violates this forum's Statement of Purpose)
Locks a thread when the OP is not on-topic for the group. An automatic notification will be dropped into the OP explaining why the thread was locked. The thread can only be unlocked by the Host who locked it.
Lock thread (Reason not specified)
Locks a thread for an unspecified reason. An automatic notification will be dropped into the OP, but no reason for the lock will be provided. The thread can only be unlocked by the Host who locked it.
Pin & lock thread
Pins a thread to the top of the group and simultaneously locks it. An automatic notification will be dropped into the OP, but no reason for the lock will be provided. The thread can be unpinned by any Host, but can only be unlocked by the Host who locked it.
Pin thread
Pins a thread to the top of the group, where it will remain until it is unpinned. The thread can be unpinned by any Host.
Block a member from the group
Blocks a member from posting in the group. The member will be automatically notified by DU Mail. Members can be unblocked by any Host.
Make a member a Host of the group
Creates a new group Host. The selected member will be automatically notified by DU Mail. Members can only be removed as a Host by Hosts who are listed above them in the hierarchy.
Remove a Host of the group
Removes a Host. Hosts can only remove Hosts who are listed below them in the hierarchy