SEO is essentially a component of the larger category, SEM. According to Google�s Knowledge Graph, search engine optimization is �the process of maximizing the number of visitors to a particular website by ensuring that the site appears high on the list of results returned by a search engine.�
According to Wikipedia, �Search engine marketing is a form of Internet marketing that involved the promotion of websites by increasing their visibility in search engine results pages (SERPS) through optimization and advertising.� SEM includes SEO tactics, as well as several other search marketing tactics.
