Both use keyword research to uncover popular search terms. The first step for both SEM and SEO is performing keyword research to identify the best keywords to target. The research includes looking at keyword popularity to determine the top keywords or buying keywords that your ideal audience searches for. It also includes looking at keyword competition to see what other brands are targeting the same keywords and determining what you will need to do to compete with those other companies.
Optimizing a website may involve editing its content, adding content, and modifying HTML and associated coding to both increase its relevance to specific keywords and remove barriers to the indexing activities of search engines like Google ,Yahoo etc. Promoting a site to increase the number of backlinks, or inbound links, is another SEO tactic. By May 2015, mobile search had surpassed desktop search.