It is often incorrectly used as a term for all types. LOL Acronym for Laughing Out Loud. A term coined by graphics programmers to refer to a technique of shrinking file sizes by giving away some precision of detail. JPEG is the most common of these. By reducing the so-called quality of a picture when you save it, you can make the file size smaller.
Many pictures can take a lot of loss of fine detail before it becomes noticeable on a web page.
Newcomers are encouraged to lurk for a while as they get the feel of things. A user who is a loser. The result of a dispute at MIT some years ago where computer error messages referred to errors by users. Others changed users to losers, and the dispute continued until someone coined the term lusers, which everyone liked. Lynx A text-only web browser that was an early workhorse before the web gained its graphical face.