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

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

Tiered link building uses two levels of backlinks to boost your site’s ranking. Tier 1 links point directly to your site and carry the most weight. Tier 2 links support those Tier 1 links, helping them appear stronger to search engines