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

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 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