This article breaks down how tiered link building works by using Tier 1 links...

https://travissinsightfulthoughtss.theglensecret.com/how-do-i-tell-if-a-backlink-is-relevant-or-just-high-da-fluff

This article breaks down how tiered link building works by using Tier 1 links to boost your main site’s authority and Tier 2 links to support those Tier 1 pages