hyperlink (or link) is a reference to data that the reader can directly follow, or that is followed automatically.
A hyperlink points to a whole document or to a specific element within a document. A hyperlink has an anchor, which is the location within a document from which the hyperlink can be followed; the document containing a hyperlink is known as its source document. For example, in an online reference work such as Wikipedia, many words and terms in the text are hyper linked to definitions of those terms. Hyperlinks are often used to implement reference mechanisms, such as tables of contents, footnotes, bibliographies, indexes, letters and glossaries.