From the About page:

This website is a proxy service that exposes gemini:// servers (and other hipster protocols, collectively referred to as the "smolnet") over the web so they can be accessed in a normal web browser.

And if you're wondering about what gemini:// is, Wikipedia has an article, but it's basically HTTP/HTML/JS/CSS stripped down to the absolute basics as an attempt to get rid of all the BS that has accumulated due to the corporate influence over the years.