Link Tags can take you to other web pages or to locations within the current form. They are a huge part of this tutorial, so you've probably seen these tags for a while now.
Optional parameters are url, mark, and memo "url" is the complete web address (including http://). "mark" is used for internal links. "memo" is the text to be displayed.
Note for example below: To switch views between the Active Form and Markup Code, click on "View" in the upper right of this page. Then choose "Form" to see the Active Form or choose "Markup" to reveal the Markup Code.