What is Followback.biz?
Followback was created to help users follow those who follow them. The great thing about this is that its done for you automatically, so when somebody follows you, you can follow them back while your in work or asleep. But wait there's more, if somebody unfollows you, we will unfollow them for you. Making sure that your Following / Followers ratio is kept even.
What are the advantages of this? Using this tool will ensure that you dont lose new followers that follow you and then unfollow you because you didnt follow them back. (There is no rule that says you have to follow somebody back, but its a courtious thing to do and people often get offended if you dont follow them back, especially if they show a keen interest in the pictures you upload)
In summary: The concept is simple, its just a way to show some courtesy to your followers by following them back and allowing you to see what your fans are doing on Instagram.