Hard to explain. They NYTimes has an article which says
What seems to separate randonneurs from bike-path cruisers is as much mental fortitude as physical stamina. “It’s a whole different spirit,” Ms. Pineda later explained. “The kind of people who do these kinds of things are always in a good mood.”
In a short post this Spring, VeloOrange says this on randonneuring:
Randonneuring is centered around endurance cycling – riding comparatively long distances. The events are timed, and in order to qualify, a rider has to prove that they completed the ride (brevet) within the time allotted. Riders are seriously interested in qualifying, because the rides are preliminaries to a Grand Randonée, and this year Paris-Brest-Paris overshadows all others. Americans seeking to participate in a 1200k ride like PBP will need to complete a 200k, 300k, 400k, and 600k brevet within the time limits.
And the LazyRando tells one how to navigate a Brevet, the starting distance.
Now, next year all I have to do is join and get going!