In the Greek, "agape" is unconditional love, one that is spiritual and selfless. "Phileo", on the other hand, is the love that one would feel for a brother or close friend. In the English of John 21, we lose an important distinction between these two Greek words. ...
Have you read the article Sloppy Agape
at the site for the International Standard Version? It presents the words agape
as interchangeable and far more versatile than they are made out to be in comments about John 21: 15-17.
Using Strong's Concordance, we can see that the verb agapao
even appears where we read of the "love" of Demas and Balaam:
for Demas has forsaken me, having loved this present world ... ( 2 Timothy 4: 10 ).
They have forsaken the right way and gone astray, following the way of Balaam the son of Beor, who loved the wages of unrighteousness ( 2 Peter 2: 15 ).