Search engine optimization (SEO) is the process of improving a website to increase its visibility in search engine results. SEO involves optimizing aspects of a website both on-page, like content and internal links, and off-page, like external links and social media, to help search engines understand what the site is about and determine its relative importance. Proper SEO can help drive more visitors to a website through organic search results and increase sales and brand awareness for businesses. Key factors that influence search engine rankings include content quality and quantity, site speed, easy navigation, and link popularity.