Tiered link building uses two levels of links to boost your website’s ranking....

https://blogfreely.net/paige-coleman3/guest-posting-for-tier-1-links-what-should-i-watch-out-for

Tiered link building uses two levels of links to boost your website’s ranking. Tier 1 links point directly to your site and are high quality. Tier 2 links support Tier 1 links, helping to strengthen their impact