A Group Tag can be used to mark an offer and/or affiliate that belongs to the same group. For example, please consider the following case:
Offer 1895 - Game Review Magazine can only be marketed by affiliates who are bloggers.
You can tag an offer and affiliates who are bloggers with Blogger tag.
On your campaign list, you will see that the tag will be green-bordered if the affiliate and its offer belongs to the same tag group. Otherwise, the tag will be red-bordered.
In this case, you know that the offer is suitable for the affiliate to run, and you can just easily approve the request.