SEO, or search engine optimization, is the process of optimizing a website or online content to improve its visibility and ranking on search engine results pages (SERPs). It involves various techniques and strategies, such as keyword research, on-page optimization, technical optimization, link building, and content creation, with the goal of increasing organic, non-paid traffic to a website from search engines. SEO helps businesses improve their online presence, attract targeted traffic, and ultimately drive more conversions and revenue.