Most photo files on the Internet and elsewhere are JPEG files, usually files ending .jpeg or .jpg. It's a *lossy* format for photographic images - can be used for any sort of graphics, really, but it's best for photos. Lossy? Yes, it's a file format that actually loses some data. With photos, you can get away with losing some of the data without it being noticeable to our eyes. And the result is much smaller files with very little noticeable drop in quality. Jpeg images have some pretty strong advantages: * They're much smaller than non-lossy files, while still looking the same. * They're very widely supported - almost every digital camera ever made outputs Jpeg images, and pretty much every computer/OS/device that can display images, from the last couple of decades, can display them. There are more modern file formats, like WebP and HEIF, that are even smaller, but not yet as widely supported. Since we're talking about photography here, though, the other major file format that most decent cameras can capture is called RAW. Jpegs win over RAW files for being much better supported for viewing elsewhere, and being much smaller. But the RAW files hold a lot more data that's already been lost when the camera generated a Jpeg image. See also: [[RAW]].