SEO (Search Engine Optimization) is the practice of optimizing websites to improve their visibility on search engines like Google. It involves on-page SEO (content optimization, keywords, meta tags), off-page SEO (backlinks, social signals), and technical SEO (site speed, mobile-friendliness, structured data). Effective SEO enhances organic traffic, boosts rankings, and increases conversions. Key strategies include keyword research, quality content creation, link-building, and optimizing for user experience. Regular algorithm updates require continuous monitoring and adaptation. SEO is a long-term strategy that, when executed correctly, can significantly enhance online presence, brand authority, and business growth.