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

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

Tiered link building uses two levels of links to boost your site’s rankings. Tier 1 links point directly to your main pages, driving real traffic and authority. Tier 2 links support those Tier 1 links, making them stronger and more effective