Aluminum foil that's food grade will have coatings on it to assist with food release. I assume that's part of why one side is more shiny than the other.

It'd be coated, but it's from processing, cold rolling metal generates a lot of heat, especially going that thin (thinnest I was around often was ~0.2mm), we'd often temper the material after processing, mainly for surface finish, mill rolls would be sprayed with lubricating coolant really close to what you'd see in use on a milling machine. This was with steel but same principle applies, pretty sure the lubricant we used is also labeled for use on aluminum mills, but you'd use food safe stuff for kitchen foil.