Usually real friends are closer than pen friends, but that is not always true. The main difference is what activities are available. I might go out to a bar or a movie with a real friend. That is obviously impossible with a pen friend (or pen pal, as we say in the U.S.). I could discuss a film with a pen friend, but I couldn't see it with them. I guess we could stream the film at the same time over the internet, but it still wouldn't be quite the same thing as watching it together in person.

I have a coffee cup full of friendly pens. There are: Bluey, Blackie, Markero, and Highlighty. I often chat with them!

Sometimes people meet their penfriends after a few years of corresponding and they become real friends, even though they may not live in the same country. I would prefer real friends whom I could go out with and talk to face to face.

With real friends there is a 3D encounter , there is too much to share ,while with pen friends it is really limited,but could be a good way to find someone to talk and listen to.They remain however always potential real friends,if the chance ever come and they could meet.

I think they are different concepts, but not necesarily incompatible. A pen friend is someone whom you write to in a casual and friendly way, about all kind of subjects. A real friend is someone who shares a part of your life, who can help in any situation, and who is always there to make good and bad moments kind of better. So may be the case that a pen friend happens to be also a real friend.