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

https://wiki-spirit.win/index.php/What_Does_%E2%80%98Natural_Link_Growth%E2%80%99_Look_Like_for_a_Tiered_Campaign%3F

Tiered link building uses two levels of links to boost your site’s ranking. Tier 1 links connect directly to your site from trusted sources, giving strong SEO support