Search Engine Optimization (SEO) refers to techniques used to improve a website's visibility and rankings in search engine results. Effective SEO involves optimizing elements like keywords, content, links, and site structure to help search engines understand what the site is about and determine its relevance to specific search queries. Key aspects of SEO include on-page optimization of titles, meta descriptions and content, as well as off-page activities like link building and social media promotion. The goal is to increase organic traffic and rankings by having the website appear higher in unpaid search results.