M arkup L anguage. HTML is the language used to tag various parts of a Web document so browsing software will know how to display that document's links, text, graphics and attached media. Each word processor uses its own format. These documents are difficult to exchange with other word processors. HTML documents are plain text, with special tags to describe the document structure.
Web browsers use the HTML tags to determine the structure of the content on the page.
HTML documents are not dependant on Operating Systems, but there is some variety on how a HTML document will look that depends on Operating System and Web browser. The monitors used by Wintel and Macintosh machines are different. Color Tables for Unix, Wintel, Macintosh machines are different. And, various Web browsers may display headings or text in different point sizes and fonts. So, the appearance of a HTML document can vary.