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

https://delta-wiki.win/index.php/What_Anchor_Text_Should_I_Use_for_Tier_1_Links_Without_Overdoing_It%3F

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