This is the description of the group-representations tag:
Use as a synonym to the representation-theory tag
So we may want to merge them together already.
Representation theory is more general than group representations as it e.g. includes Lie algebra representations.
I have just made the group-representations tag a synonym of the representation-theory tag. (It was proposed in 2016 with currently 1 upvote.) Depending on feed-back from the community, we can later merge or undo the synonym.