I bet you haven't seen one of these in a while, webrings!
A webring is a collection of websites linked together in a loop, usually targeted at a specific theme or category, often educational or social. Each webring has it's own "navigation bar" to navigate around the webring, most have a previous and next button, each taking you back and forth respectively. Webrings were often used as an alternative to using SEO, because it allowed for people to easily find other sites in the same category.
Webrings were mostly around in the 1990s, but even nowadays you will still find some.
Below you can find the webrings I'm in!