HyperText is a term coined by Ted Nelson in the mid-sixties that describes non-sequential writing on screen. It aids nonlinear, spatial, and associative thinking/notation and is practical only via computer media.
HyperText is a forerunner concept of Hypermedia and >HyperCard<.
Alan Boyd of Owl International developed Guide as the first working hypertext product for the Mac until >XrefText< was written for HyperCard by >Frank Patrick<.
For more information on Hypertext, see Literary Machines, a book by Ted Nelson available in a standalone Guide Envelope format from Owl International (hypertext in hypertext).
Also, in more traditional format, Nelson's amazingly up-to-date 1974 book, Computer Lib/Dream Machines has been republished by Tempus Books on portable, non-volatile, read-mostly, cellulose-based media (paper).