Wikipedia: A webring is a collection of websites linked together in a circular structure, and usually organized around a specific theme, often educational or social. They were popular in the 1990s and early 2000s, particularly among amateur websites.
Methods of website linking - In the field of search engine optimization, link building describes actions aimed at increasing the number and quality of inbound links to a webpage with the goal of increasing the search engine rankings of that page or website.
Web directory - A web directory or link directory is a directory on the World Wide Web. A collection of data organised into categories It specializes in linking to other web sites and categorizing those links.
Article directory - An article directory is a website with collections of articles written about different subjects. Sometimes article directories are referred to as content farms, which are websites created to produce mass content, where some are based on churnalism.