Especially in the context of online interaction. How would one define the difference? For me Facebook blurs the issue every contact is labelled a ‘friend’ and yet the strength of the relationship varies from contact to contact . Some people you have met in real life others only online.
I have people I get on with , but to me it needs something more than that to classify them as friends although they may be good people that I like and respect.
I agree that a friend is someone extra special. You can tell them anything, you can always rely on them. You trust each other. You enjoy each other’s company. You like an acquaintence, but you love a friend.
To me, a friend is someone you can contact in the middle of the night and they’ll gladly help you.
A friend knows things about you that you wouldn’t tell just anyone, and you trust them.