Search Engine Marketing (SEM) is a smaller part of SEO and refers to the process of getting your website on a SERP (search engine ranking page); it focuses on getting visitors onto your website. SEM also refers to PPC (pay-per-click) and paid searches.
Search engine marketing (SEM) involves marketing a business through the use of paid advertisements and using keywords and phrases throughout the content. It primarily refers to the use of search engine advertising (SEA) through the use of pay-per-click ads. However, an SEM campaign can also include SEO, which can increase the chances of website content appearing higher on the search engine results page organically.