SEO
Also known as: Search engine optimisation
SEO is the practice of making a website more likely to appear in unpaid search results for relevant queries.
In full
SEO, or search engine optimisation, is the practice of improving a website so that search engines rank it highly in unpaid results for queries relevant to the business. It has three broad components. Technical SEO concerns whether a search engine can crawl, render, and understand the site at all. On-page SEO concerns whether the content genuinely answers the query behind the search rather than merely containing the words. Off-page SEO concerns whether other credible websites reference yours, which search engines read as a signal of standing. SEO is a probabilistic discipline rather than a deterministic one: no practitioner controls the ranking systems, so no practitioner can guarantee a position.
Why it matters
Unpaid search remains one of the largest sources of commercial intent traffic on the web, and unlike advertising it does not stop the day you stop paying. The compounding nature is the point: a page that ranks keeps earning.
A common misconception
That SEO is a one-off task. Search results are competitive and continuously re-evaluated, so a site that stops improving loses ground to sites that do not.