Tier 1 links are your direct authority boosters while Tier 2 links help them...

https://www.first-bookmarkings.win/tiered-link-building-helps-pass-authority-efficiently-by-connecting-tier-2

Tier 1 links are your direct authority boosters while Tier 2 links help them stay relevant. Using Ahrefs to monitor your backlink profile helps you see how these layers push rankings up without overdoing it