Well, first of all, I could be wrong. I'm surprised no one with more knowledge has chimed in yet.

Basically, though, think of it as a way to make a slide out of a non-film image (or after manipulating something electronically). Kind of the reverse of scanning.
Lets say you made a graph with computer software and wanted to put it on film for some reason. You could use a "film printer" to make a slide out of it - by "printing" it to film. Whether the film in question is actually optimized for this, or merely marketed as such, I do not know. Even if "optimized," I would imagine it would work in the traditional manner after some testing to dial it in.