In Hyper-G and possibly other hypertext systems, a link type is the specification of the nature of the information object being linked to. A single link can have any number of defined link types. For example, for any word from which one might link to another information object, that object could be an example of that word, or a graphic illustration of it, or a definition of it, or it might be associated with one person's comments on that subject.
For example, in a page on transmission technologies, the term "ISDN" might be highlighted as a link. When the link is created, the author might choose to let the reader link to an illustration of how ISDN works, or just a brief definition of it, or a whole book about it. Or a reviewer (rather than the author) might create the link for review purposes and the link would be to a particular reviewer comment. (Later, the author or other reviewers would find the link and the linked-to comments and perhaps create additional comments.)
If link types are made generic and all links exist as separate objects apart from the files in which they are used, then different link types and links can be easily added, removed, or changed throughout a set of files.
The examples described here are hypothetical and not necessarily exactly how Hyper-G or any other hypertext system works.