What do you think the difference between friend and follower here?

The follower has sent you a friend request, and you've allowed them to remain a follower. It probably means you have no objections to them, but they don't interest you enough that you'd want to reciprocate.

The friend is someone you've friended back; it's mutual.
I take it as a sign of mutual admiration, liking and respect.

In both cases, it doesn't necessarily mean that there is any other communication between the two people.

Friend is mutual following.

A real friend send me nudes.