Yes, it’s random firings of light receptors from the absolute ocean of potential stimulators for such sensitive cells and such sensitive neurons that connect them to your brain.

Your brain does a profoundly involved job at every moment editing your visual input into a coherent, moving picture, but your brain edits out a LOT of interference and noise every moment.

If you really wanna blow your mind and prove it, make a pinhole in a card and in a dark room and look towards a light source. If you wiggle the pinhole light beam across your retina you will suddenly see all the blood vessels that feed your retina. Evolution decided it would put them on the front for some reason, but your brain normally makes it literally disappear for you. When you wiggle the shadows of the vessels, your brain forgets how to edit it and they appear like a mass of floater-spaghetti.