SEO Course in Delhi Search engine optimization (SEO) is the process of affecting the visibility of a website or a web page in a search engine's unpaid results—often referred to as "natural," "organic," or "earned" results. Search engines are said to rank websites according to the relevance and quality of their content, how often they are linked to other sites, how well they match the search query, and any other factors that may improve their rank. For websites to be found by users, they need to have sufficient levels of traffic from search engines. One way is through SEO.