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

https://smart-wiki.win/index.php/Is_Domain_Authority_(DA)_Still_a_Good_Metric_for_Link_Building%3F

Tiered link building uses two levels of backlinks to boost your site’s authority. Tier 1 links point directly to your site and carry the most value. Tier 2 links support Tier 1 by linking to those backlinks, increasing their strength