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

https://www.4shared.com/office/BIObF2h6fa/pdf-72309-44204.html

Tiered link building uses two levels of links to boost your site’s authority. Tier 1 links point directly to your pages and carry the most weight. Tier 2 links support Tier 1 by linking to those pages, strengthening their impact