Tiered link building boosts your website’s authority by using multiple layers...

https://www.bookmarkmaster.win/tiered-link-building-uses-two-levels-of-backlinks-to-boost-your-site-s-1

Tiered link building boosts your website’s authority by using multiple layers of backlinks. Tier 1 links point directly to your site, while Tier 2 links support those Tier 1 sources