Tiered link building helps boost your website’s authority by layering links....

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

Tiered link building helps boost your website’s authority by layering links. Tier 1 links point directly to your site, giving it strong, high-quality signals. Tier 2 links support those Tier 1 links, making them more powerful and natural