Tiered link building boosts your site's authority by building links in layers....

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

Tiered link building boosts your site's authority by building links in layers. Start with Tier 1 links from trusted, relevant sites that point directly to your page. Then, support those with Tier 2 links that strengthen your Tier 1 sources