Links are obviously a huge part of how the internet works. When you click on a link, you either go to another web page or document, or to another position within the same document (referred to as a bookmark then, not really a link). The format of a hyperlink is:
<a href="URL of what you are linking to . . . ">Linked text that displays</a>
You generally have 3 choices for the "URL of what you are linking to . . . ": within the web page itself (bookmark), to another page or document on your site (internal or relative), or to an external (or absolute) page or document.
You might notice on the link to AHS that there's a little bit extra in the a href part, target="_blank". I added that because Trinket doesn't like to open external websites within the Trinket window, but it will open a new tab or window. The target attribute specifies where you want the link to open. By default, if you don't specify anything, a link will open in the same window - meaning it replaces the page you are currently looking at. You can, however, specify this (since users can set their browser to do different things by default). The value of the target is always enclosed in quotation marks.
_self Opens the linked document in the same window/tab as it was clicked (this is default)
_blank Opens the linked document in a new window or tab
_parent Opens the linked document in the parent frame
_top Opens the linked document in the full body of the window
framename Opens the linked document in a named frame
We'll see on the next page that you can also use images as a link instead of just text.