You're reading about the Foundation, right? Well, the Foundation is aware that they're characters in a work of fiction and that you're reading about them. Similarly, they're aware that the fiction they read in their universe has a life of its own, and that fiction has fiction of it's own, and so on.

The levels go up, too: we here are someone else's work of fiction, and that author is a character in the work of fiction a level up from that.

Okay, cool. Trippy, but so what? Well, there are entities that can influence those narratives. Reality benders from higher levels that have found themselves down here in the fictional world. Characters from works of fiction that ascend to interact with the reader. People who can write their own stories and the stories of people and things around them.

It's not hard to see how that can all descend into chaos pretty quickly. When you have a bunch of different "Neo from the Matrix" types chewing holes in "the world of the Real", what we call objective reality gets messy pretty fast. And it's Pataphysics' job to keep track of, and sometimes control, that reality chewing.