Tiered link building uses two levels of links to improve your site’s ranking....

https://landensinsightfulperspectives.wpsuo.com/what-should-i-do-if-my-tier-1-backlink-disappears

Tiered link building uses two levels of links to improve your site’s ranking. Tier 1 links point directly to your site and are high-quality. Tier 2 links support those Tier 1 links to boost their power