This page is a demonstration of how NOT to use the <iframe> tag.
Normally, this tag is used by developers to embed websites within other websites. On this portfolio site for instance, I use them to embed Desmos graphs on the Desmos project pages.
That way, you can interact with the graphs without leaving the page.
But what if you embedded a website within itself? Well, you'd get exactly what you're seeing above.
Better leave this page before your browser crashes... there is not a cap on the recursion!