Tiered link building uses two levels of backlinks to boost your site’s search...

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 backlinks to boost your site’s search rankings. Tier 1 links point directly to your website and have the most value. Tier 2 links support your Tier 1 links, making them stronger