When using the web, we use hyperlinks all the time. In fact, hyperlinks are the core experience of the web, where we can move from one page to another by clicking a word or a phrase that has been highlighted by an underline or a different color.
Click, click, click - we move from page to page by links, following a path of discovery.
These hyperlinks are a feature of Hypertext 
. All web pages are created using a language that was developed to support hypertext, called Hypertext Markup Language (HTML) .
Hypertext is the foundational language of the web and creates new possibility for something we might call a Hyperbook.