Search Engine Optimization (SEO) is the practice of improving website visibility and rankings in organic search engine results, primarily Google. It encompasses technical implementation, content strategy, and authority-building to help search engines understand, crawl, index, and rank web pages. In 2026, SEO has evolved beyond traditional search to include AI-powered answer engines, voice assistants, and generative search experiences — making structured data, user intent alignment, and E-E-A-T (Experience, Expertise, Authoritativeness, Trustworthiness) more critical than ever. A key mental model: search engines reward content that best satisfies user intent, not just keyword optimization — your job is to demonstrate relevance, authority, and value through both on-page signals and external validation.