A hyperlink, is a reference or navigation element in a document to another section of the same document or to another document that may be on a (different) website.

A link has two ends, called anchors, and a direction. The link starts at the source anchor and points to the destination anchor. A link from one domain to another is said to be outbound from its source anchor and inbound to its target.

The most common destination anchor is a URL used in the World Wide Web. This can refer to a document, e.g. a webpage, or other resource, or to a position in a webpage. The latter is achieved by means of a HTML element with a "name" or "id" attribute at that position of the HTML document. The URL of the position is the URL of the webpage with "#attribute name" appended — this is a fragment identifier.

When linking to PDF documents from a HTML page the "attribute name" can be replaced with syntax that references a page number or another element of the PDF, for example page=[pageNo] - "#page=386".