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

https://www.tumblr.com/powerfullyskeletaltrail/823644826747731968/guest-posting-for-tier-1-links-what-should-i

Tiered link building uses two levels of backlinks to boost your site’s ranking. Tier 1 links point directly to your pages, driving real traffic and building authority. Tier 2 links support Tier 1 by linking to those backlinks, making them stronger