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

https://www.booknose.win/tiered-link-building-uses-two-levels-of-links-to-boost-your-site-s-seo-tier-1

Tiered link building uses two levels of links to boost your site’s ranking. Tier 1 links point directly to your site and carry real weight. Tier 2 links support those Tier 1 links, making them stronger and more effective