It is an expression coined by Theodor H. Nelson in the Sixties. It is a type of electronic text, a radically new computer science technology and, at the same time, an edit mode.
The hypertext deals about a type of text that branches off, that have different ways to be able to be read. It is a series of connected text blocks to each other by nexuses, that form different itineraries for the user.
The reader of hypertexts must choose between the different ways that this kind of texts offers. And whenever he reads it and he chooses a different way, he will arrive at different end, and to different conclusions.
The most outstanding effect is that it releases the literary text of the determinism psychological, sociological and historical, opening it to an apparently infinite range of relations.