WordPress is a content management system. Such content management systems can be used to host your own website. Or you can rent some space and service from others and host your site. So for example WordPress.org gives you the CMS for free and you can host your content on your own server. And in case of WordPress.com you can rent some space and features per month on some fee.
WordPress is developed in PHP which you can modify if you host CMS on your own server. Most of the blogs are designed in PHP and so for that reason they are on WordPress. Apart from WordPress some other CMS are used as well such as Drupal, Mambo, Livejournal, Blogger etc. So it's not like all websites are in php with CMS like WordPress.
That's the difference between each of these services.
In case of ISC, it is made up of it's own CMS developed in ASP.Net. So the CMS is specific to this site. And the hosting and the domain expenses are from the website owner himself. It is not like WordPress or any other blog.
Note: No matter how you design website (with or without php like wordpress) you need hosting and domain. And if you get it from some service like WordPress.com then you have their fees for everything. If you design your own theme and blog in WordPress then you have to just buy hosting and domain.
I hope this clears your doubt on self hosting and hosted platforms websites.