Search Engine Optimization (SEO) is the process of optimizing a website to improve its visibility on search engine results pages (SERPs). The goal is to increase organic (non-paid) traffic by aligning with search engine algorithms. Key aspects include keyword research, on-page and off-page optimization, technical SEO, user experience, content creation, local SEO, and analytics. SEO is an ongoing effort to adapt to evolving algorithms and maintain or improve search rankings.