All the indistinguishable photons illuminate the array of N slits, or grating, simultaneously. If only one photon propagates, at any given time, then that individual photon illuminates the whole array of N slits simultaneously.

What It Means

This is a placeholder explanation generated by the low-overhead model. It interprets "All the indistinguishable photons illuminate the array of N slits, or grating, simultaneously. If only one photon propagates, at any given time, then that individual photon illuminates the whole array of N slits simultaneously." in the context of "F. J. Duarte (2003), Tunable Laser Optics page: 26, publisher: Elsevier Academic, ISBN: 0-12-222696-8" to mean that wisdom is timeless.