Search engines rank websites by evaluating factors like content relevance, site quality, user experience and authority. For national SEO, rankings depend heavily on content depth and quality, backlinks and overall site strength. Local SEO adds elements like proximity, Google Business Profiles and local citations. For ecommerce, search engines also look at product page optimization, your product feed into Google Merchant Center, structured data and site performance. While the core principles are similar, ranking factors vary based on your business type and audience.