There are so many different image file types these days, and unless you work with the regularly, chances are they can become confusing. Here's a brief rundown of what's what and what you should use the for. The JPG: Probably one of the most commonly used files on the Internet. A jpg is a compressed image file. The compression can be adjusted, so the more compression the smaller the file, but also the poorer the quality. It's also what's known as a lossy format. In other words