simple explanation of code for an external link

Here’s their explanation.

In the case of an external webpage you merely need to specify the URL to display. In this case we are using the class method for instantiating the lightbox. When the user clicks the link instead of redirecting the browser to another page it opens the page within the lightbox.

External Content (Iframe/Direct Link To WordPress plugins)

Do you put your own location for the lightbox-plus plugin on the first url? What is “External content”? Is that the url where you want to go?. What is (Iframe/Direct Link To WordPress plugins)?

I have two urls. One is the actual page http://Leadershipskills.SuccessTelevision.biz. I want to launch a login page inside a lightbox and not leave the previous page: http://site.successtelevision.biz/registration/include/register.php

Again, any help would be greatly appreciated.