The basic format for a link is:

<a href="address" 
  title="address and/or description of the file">
  Text for the Link</a>

The <a is the link element, and needs the end tag </a>.

The "href" attribute specifies a Web resource, and can be to a Web page, image file, sound file, PHP page, CGI, etc., either at your hosting space, a target location in a Web page, or anyplace on the WWW.

Realize that when you link outside of your hosting space, the possibility exists that the source will not be there tomorrow. Therefore, it's important to keep up on your links, and make sure they are still active on a regular basis.

Also realize that you are sending someone away from your site with external links, and sometimes they don't return. It's probably not a good idea when you're trying to sell something.