Link Building
Link building is the work of earning links from other websites to your own. Each backlink works as a recommendation: the more relevant and trustworthy the pages pointing at a domain, the more authority search engines assign it, and the better its pages can rank. That places link building among the disciplines in SEO with the largest effect on rankings.
The recommendation logic goes back to Google's origins and still holds. Two things decide what a link is worth: the authority of the site giving it and the topical relevance between the two. A single link from a recognized trade publication in your industry weighs more than a row of links from unrelated directories, which is why quality counts for more than quantity.
The work itself spans a wide range. At one end sits content good enough that others link to it unprompted: original data, research and thorough guides. At the other sits the outreach side, from digital PR to conversations with relevant publishers. What the durable methods share is that the link makes sense for the site placing it. Bought links at scale and private blog networks break Google's spam policies and can cost more than they ever returned.
Authoritative mentions have taken on a second function in the AI era, since the sources AI assistants lean on are largely the same trusted sites that good link building builds relationships with. The guide to link building goes through the methods one at a time.