Tiered link building uses two levels of backlinks to boost your site’s ranking....

https://wiki-cable.win/index.php/Is_Four_Dots_a_Good_Option_for_AI_SEO_Services%3F

Tiered link building uses two levels of backlinks to boost your site’s ranking. Tier 1 links point directly to your site and carry the most weight. Tier 2 links support those Tier 1 links, helping them appear stronger to search engines