SGML (Standard Generalized Markup Language) is pretty much the very roots of HTML (Hyper Text Markup Language). This language known as SGML was developed because a lot of big name companies were having the worst time trying to get their documents to look the same and work the same across multiple platforms of operating systems and hardware. So let's say that you have a report on The History of Kleenex (bare with me here), sure you have some nice little pictures, maybe an animated image of someone sneezing, the font is 22 (if you're a teenager doing a report at the last minute, believe me, the font is 22 all the way through), and just to get a little more detailed you have a left margin of 1 inch, a top margin of 2 inches, and a right and bottom margin of .5 inches. Let's stop there, I'm getting off the point of the SGML thing. Alright, you want your report to be like that in all the computers handling that. Of course, most of you know that a MAC's version of things can be different from a PC's, Microsoft Word is different from Corel, and oh , computer fonts whether all set at 22, won't be the exact same size on each computer. And finally, that's when SGML came about. It was around the 1960s when IBM thought of this discovery and it was then referred to as GML. But like all secrets, this one got out.
GML creators (Ray Lorie, Charles Goldfarb, and Ed Moster) got together and realized that a general version of markup would make documents travel-easy across a lot of platforms and hardware systems. This idea gave birth to SGML and is now popularly used today. It is currently covered by the ISO 8879 standard.
To explain this better, what SGML is doing is letting you make the preferences that can be used to define other documents to get that report looking the same across platforms, hardware systems, Networks, et cetera.
This language is way more harder than HTML and really only needs to be used for sites that are huge, we're talking over 1000 pages here.
The basic idea of SGML is to let your document stay consistant in appearance and definition.
