If you are linking to an element with a title, such as a chapter or section, the simplest way to do so is with the <xref> element. When you use <xref> to create a link, you specify the ID of the topic that you want to link to. The title of the topic is inserted in place of the <xref> element and becomes the active hyperlink.
Hypertext links created with <xref> display the new topic in the same window. If you desire different behavior by using the other link types, then you must use the <link> element.
Also, you cannot use <xref> to jump to topics that have built-in IDs (such as <hometopic> or <glossary>). To create a hyperlink to any of those elements, you must use the <link> element.