Many programs give you the ability to view the exif data of a photo. According to Wikipedia is the Exchangeable image file format (officially Exif, according to JEIDA/JEITA/CIPA specifications) a standard that specifies the formats for images, sound, and ancillary tags used by digital cameras (including smartphones), scanners and other systems handling image and sound files recorded by digital cameras. With it you can view with what camera the photo has been made, the shutter speed, the diaphragm etc. etc.
This can be done with most image viewers and photo editing software like Gimp. But it can also be done with the the command line interface (cli) with the command exiv2. Really necessary? No, but on the other hand it gives you more information than most programs.