How Nav link work for PageView.aspx?img=0&MID=35&Main=14

Hi,

I am trying to understand how the navigation link in the right is working. when a user click on any
link, the URL address shows this >>> http://www.prutech.com/PageView.aspx?img=0&MID=35&Main=14
and the page shows.  What I know is to create a link like this once clicked it shows

http://www.prutech.com/Page1.aspx
http://www.prutech.com/Page2.aspx
http://www.prutech.com/Page3.aspx

so I end up with 3 pages.

I appreciate your explanation.

thanks

Bob