If you have different domains leading to the same DNN portal and you want to start with a different landing page for each domain, this is your module.
You can place it on your homepage and define in the settings which domain alias should lead to which page. If you have more then one redirection, simply add more of this modules to the page:
You only see the module on the page if you are Admin and if you are in Edit mode. Normally the module is hidden.
The module uses a 301 redirection (permant redirection) which is important for SEO issues, because search engines don't follow a 302 (temporary redirection) redirection which is normally used by Response.Redirect(...)