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

https://reidsinterestingthoughts.timeforchangecounselling.com/how-do-i-use-social-bookmarking-without-getting-spammy

Tiered link building uses two levels of backlinks to boost your site's authority. Tier 1 links point directly to your site and carry the most value. Tier 2 links support those Tier 1 pages, helping them rank higher