Backlinks can help SEO by giving crawlers paths to discover URLs and by providing context about how pages on the web relate to one another. Google also uses link-based systems, including PageRank, as part of ranking, but it does not publish the value of an individual link or guarantee that a particular placement will improve a page's position. Discovery is the most direct mechanism. A crawler can encounter a link on a page it visits and add the destination to its known URL set. That does not guarantee when the destination will be crawled, whether it will be indexed, or whether it will rank. Sitemaps and internal links provide additional discovery paths. Context comes from the source page, surrounding copy, anchor text, destination, and the reason the link exists. A relevant citation may help readers and systems understand the relationship between two resources. Relevance should not be reduced to a rule that links from an unrelated topic have no value; referral audiences and broader editorial context can still matter. Link attributes also affect interpretation. Google treats nofollow, sponsored, and ugc values as hints. Paid placements should be qualified with sponsored or nofollow, and user-generated links can use ugc. An unqualified link is not automatically an endorsement with a predictable amount of “equity.” The safest way to earn useful links is to publish material people have a genuine reason to cite, contribute expertise where editorially appropriate, and promote resources to relevant audiences. Avoid buying links for ranking purposes, automated link creation, excessive exchanges, or manipulative anchor-text campaigns because those practices can conflict with Google's spam policies. Measure referral visits, qualified actions, new referring pages, and broader search visibility without assigning causation to one link. Backlinks can support discovery, context, reputation, and referral traffic, but their effect depends on many systems and cannot be expressed as a fixed count, quality tier, or timeline.