SEO
Search Engine Optimization — the practices that increase a website's visibility in the unpaid results of Google and other search engines.
SEO (Search Engine Optimization) is the discipline of earning organic (unpaid) traffic from search engines. It rests on three pillars: on-page (content and page structure), off-page (links and authority) and technical SEO (speed, indexability, site structure).
Why it matters
Organic results are the cheapest and most trusted traffic over the long run. Unlike PPC, you don't pay per click — a position you've earned keeps sending visitors for months or years.
Real-world example
An outdoor-gear retailer publishes an in-depth guide, "how to choose a sleeping bag". With solid on-page SEO and backlinks it reaches page one of Google and brings in buyers with no ad spend.