Tiered link building boosts your site’s authority by using two levels of links....

https://telegra.ph/What-Should-I-Use-for-Tier-1-Links-if-I-Want-to-Rank-a-Landing-Page-07-31

Tiered link building boosts your site’s authority by using two levels of links. Tier 1 links point directly to your site and should be high quality. Tier 2 links support those Tier 1 pages, making them stronger in search rankings