Photos carry more than the picture. Most phones record where you were standing, what you shot it on and when — and it travels with the file. Drop one in to see what's hiding in it, then save a clean copy.
GPS coordinates, camera and lens details, serial numbers, timestamps, editing history and any embedded comments. The picture itself is not touched or re-compressed — the extra records are simply lifted out, so the image quality is identical to what you started with. Colour profiles stay put so nothing shifts on screen.