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

https://seo.edu.rs/blog/how-do-i-build-tier-2-content-that-looks-natural-and-not-forced-11162

Tiered link building uses two layers of links to boost your site’s ranking. Tier 1 links point directly to your main site, adding strong authority. Tier 2 links support those Tier 1 links, making them more powerful