SEO (Search Engine Optimization) is the practice of earning traffic from unpaid search results. Done right, it compounds over years. Done wrong, you pour money into content nobody reads.
SEO is everything you do to make your pages rank for the search queries your ideal customer types into Google (and other search engines). Ranking means showing up near the top of the results. Near the top means clicks. Clicks mean traffic. Traffic, if qualified, means customers.
Unlike paid ads, SEO traffic is ongoing without per-click cost. A page that ranks for 1,000 monthly searches keeps delivering visitors for years. The ROI curve is the reverse of paid: slow start, steep compounding returns, long tail.
Google's ranking algorithm considers hundreds of signals, most of which are not publicly documented. The algorithm changes continuously. Competitors are also optimizing. Getting to the top of a valuable query can take 6-18 months. And it's a moving target.
The 100 pages that follow cover every major SEO topic at an expert level: foundations, keyword research, on-page tactics, technical depth, link building, content strategy, local, e-commerce, international, analytics, and emerging topics like AI in search. No fluff.