Search engine optimization (SEO) involves optimizing websites and web pages to receive free organic traffic from search engines. Key factors search engines consider include keywords, backlinks showing a website is worthy of ranking, and an optimal mobile-first user experience. On-page SEO involves keyword research, internal linking, meta tags, and title/description optimization. Off-page SEO includes link building, social media marketing, blog/article submission, and press releases to drive links and traffic. Proper web design, user experience, and content are also important for SEO.