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

https://www.bookmarkpage.win/tiered-link-building-uses-two-levels-of-backlinks-to-boost-your-site-s-ranking

Tiered link building uses two levels of links to boost your site's authority. Tier 1 links point directly to your main pages and have the most value. Tier 2 links support Tier 1 by linking to those pages, increasing their strength