The screen is the basic chunk of text.
Unlike pages in a print text, screens may be rearranged by the actions of the reader.
Thus a hypertext has no fixed structure, only one which is created by the activities of the reader.
Hypertext authors, of course, don't simply arrange the screens randomly. In fact, in some ways a hypertext is more structured than a print text. The author tries to create a text which is multiply meaningful, a text which can be explored by a reader following chosen paths from screen to screen.
Hypertexts can be mapped. A map of a hypertext will show all of the screens and all of the links or paths between them. The map represents the overall structure of a hypertext, but this will not be the structure of any single reading. A single reading will only explore some section of the hypertext. That is, a reading of a hypertext does not exhaust the possibilities of the text. Another reading can take different paths and visit different screens.
With all of these potential arrangements, how is meaning created in a hypertext?