SEO (Search Engine Optimization) is the process of optimizing website content to increase organic search visibility and traffic. It involves technical, on-page, and off-page optimization. Technical optimization focuses on website speed, structure, and indexing. On-page optimization involves headings, keywords, meta tags, images, and internal/external links. Off-page optimization uses link building and social media to improve search rankings. Free SEO tools can help with optimization, keyword research, and technical analysis. The overall goal of SEO is to have a website rank highly and earn relevant traffic from search engines.