When you've been around a person, or a group of people, for a long time, you have a lot of common experiences. When retelling those stories or recalling to the person/group the events of some day, everyone develops a bit of shorthand. A "You had to be there" sort of explanation, that only makes sense to those who were there.
For example, I can simply say "Astral Wolves" or "I am of the Dark Wood!" to my friends, and they'll know the entire context of what I'm trying to say. Or I could say "Big Damned Book of Loonies," or make a gesture with my hand passing about 6" over my head, from front to back, with a "Whoosh!" sound, and another subset of friends will smile and laugh. These, of course, are mostly gaming related anecdotes. For family, I can say to Lou "I can confirm that," or "Billy Barty," and another whole set of shared experiences are referenced.
Why do I bring this up? Because we now have a word for this shorthand, this leaving out of the story, since it's a shared experience that doesn't need repeating. With a few simple words or gestures, we know what we're talking about.
And that term is Exformation.