This article explains how tiered link building works by using Tier 1 links to...

https://isabellasbrilliantcolumn.lucialpiazzale.com/how-do-i-know-if-a-tier-1-site-is-trustworthy-before-i-pitch-them

This article explains how tiered link building works by using Tier 1 links to point directly to your site and Tier 2 links to support those Tier 1 sources