SEO is short for search engine optimization and contains a bundle of techniques aimed at the optimization of websites and webpages so they can be found better by search engines and can be ranked more effectively. Search engines use so called search engine ranking factors like on-page keywords, off-page links and page speed to award value to web pages and websites for the rankings within search results. Search engine optimization is belongs to the domain of online marketing and is a discipline of search engine marketing. Source: https://www.ensie.nl/daniel-mulder/seo Daniël Mulder also author of this faq and in Dutch only,
What is search engine optimization (SEO)?
What are on-page SEO ranking factors?
On-page seo ranking factors are all elements found on a page itself and that influence search engine rankings. The two main on-page ranking dimension are content and internal hyperlinks. Content is what is the basis on which we are ranked but without links it is impossible for search engines to discover our content. Also internal links are used to rank pages on a domain from less to more important based on the amount of internal links an URL receives. On-page SEO factors also contain all visible texts and HTML elements visible and invisible elements in the page source and pagespeed factors like caching and image and other file compression techniques.