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 carry the most weight. Tier 2 links support those Tier 1 pages, making them stronger and more trustworthy