Tiered link building uses two levels of links to boost your site’s authority....

https://ace-wiki.win/index.php/What_is_Tiered_Link_Building_in_SEO_and_Is_It_Safe%3F

Tiered link building uses two levels of links to boost your site’s authority. Tier 1 links point directly to your website and carry the most value. Tier 2 links support those Tier 1 links, helping them perform better in search rankings