Modern friends are those relationships that primarily originate and develop through digital channels (forums, email, reddit, twitter, etc).
Modern friends typically discover one another via shared personal interests, “professional” (personal development) collaboration or friend-of-friend introductions.
One mark of a strong modern friendship is the rate of which the two end up hanging out offline when they happen to be in the same place (conference, personal travel, meetup, etc).
This new type of relationship and graph is emerging. There exist dozens of individuals in your life that neither deserve being a stale node in a LinkedIn graph nor have they transitioned (yet) to being a close friend on WhatsApp/iMessage/Snap.