Backlinks are hyperlinks from other websites pointing to your site, treated by search engines as a primary signal of authority and trust. Also called inbound links, they are judged on the quality, topical relevance, and trust of the linking site, which matter far more than raw count. They are the authority pillar of SEO and the single hardest signal to fake at scale.
The taxonomy that matters: a dofollow link passes authority (PageRank) from the linking page to yours; a nofollow link includes rel="nofollow" and historically did not, though Google has treated nofollow as a hint rather than a directive since 2019. Two other attributes are relevant: rel="sponsored" (for paid placements) and rel="ugc" (for user-generated content). Lin...