Hypertext is nothing more than the inclusion of
links within a body of text. These links can be unique markers or
icons between the words or sentences, but are typically just a string of the words themselves. Selecting the link opens up a new hypertext document, or moves to a different section of the same document.
HTML is short for HyperText Markup Language, and has long been the de facto standard for formatting and displaying hypertext on the World Wide Web. You see non-HTML hypertext all the time, however -- in your CD-ROM encyclopedia, a HyperCard stack, or your Windows Help panel, and that's only on your personal computer.
It dates back to the late 1960s, when Ted Nelson proposed it as one of the then-alternative uses of technology:
By "hypertext" I mean non-sequential writing--text that branches and allows choice to the reader, best read at an interactive screen. As popularly conceived, this is a series of text chunks connected by links which offers the reader different pathways.
In June 2000, British Telecom briefly threatened to enforce a patent on hyperlinking which predated the WWW, and asked for ISPs in the United States for voluntary cooperation. Apparently they didn't get it, because their "patent" hasn't been heard about since.