Visual is different from the Face of the Group!
Visual – usually the better looking members of the group.
Face of the group -almost like the representative of the group , the first member you will actually think of, when the group is being called.
So for T-ARA:
Jiyeon is the visual. (No doubt! Eunjung, Hyomin and Qri can also be visuals, but Jiyeon have that title. Lol)
Eunjung is the face of the group. (She is the representantive of T-ARA. And she is the most popular member along with Jiyeon)
