Backlink
A backlink is a link from another website to yours. Search engines read it as an endorsement, which makes it one of the strongest ranking signals. Relevance and trustworthiness of the linking site matter far more than the raw number of links.
Why it matters for your rankings
Links remain the backbone of how Google separates pages that deserve to rank from pages that merely exist. Content quality is hard for a machine to judge directly, but a link from a respected site is a human vouching for you, at scale.
The economics are unforgiving. Links are the hardest ranking factor to acquire honestly, which is exactly why they still work. Anything cheap and repeatable, such as directory spam, paid placements or private blog networks, is cheap and repeatable for everyone, and Google has spent two decades learning to discount it. One link from a genuinely respected industry publication typically moves rankings more than a hundred from low-quality sites, and it carries no risk of a manual action arriving later.
How to check it on your site
Pull your full profile
In Ahrefs or Semrush export all referring domains. Sort by Domain Rating and skim both the top and the bottom of the list.
Identify the gap
Use a Link Intersect report to find sites linking to two competitors but not to you. That list is your most realistic outreach target.
Check for obvious toxicity
Look for sudden spikes of links from unrelated foreign-language sites or identical anchor text repeated across many domains.
Verify links are live and followed
Spot-check your best links in a browser with JavaScript disabled and confirm they still exist and are not marked nofollow.