so what is EXIF?

EXIF (Exchangeable Image File Format) is a standard format maintained by the Japan Electronic and Information Technology Industries Association (JEITA) for metadata in digital images. EXIF is used to tag image files with metadata like image width and height, bits per pixel, camera settings like shutter speed and a whole host of other image specific data like the GPS location where the image was taken, and the date and time when the image was taken. EXIF is supported by almost all modern digital cameras. It is also used to tag other types of files, i.e. sound files, PDFs, OpenOffice/LibreOffice or Word docs.