Hypermedia organizes information as an interconnected web of associations rather than as a linear sequence (which you find in a book). Scattered within a hypermedia document are hyperlinks (words or images that are highlighted) to other related documents. Clicking on a hyperlink brings up a new document. In turn, that document links to others, and so it goes.
Most documents available on Web servers are linked, meaning that hyperlinks embedded in the documents connect all the documents in some way. For example, NCSA Mosaic documentation contains links to documents on the NCSA Web server as well to documents on servers maintained by other universities and research laboratories. Those Web servers have documents that, in turn, link to other documents on other servers.