In a Facebook group, what's the difference between an admin and an officer? Thanks.

the admin is the one who created the group usually, they can appoint officers but they are basically the head honcho, revoking officer status at their whim.

creator of the group can give himself/herself and other members “admin” status. people with that status can make changes to the group description/settings etc. “officers” are really just for show and fun, they do not have any special privileges compared to regular members.