SEM is a Broader term than SEO. Where SEO AIMS To provide better organic search results, the search engines use SEM to advertise your website or business to Internet customers and send a more targeted traffic to your Web site.
For example, When people use a search engine to query "fashion handbags", the organic search engine results is where SEO technologies
can assist in your Web site being more visible. The paid advertising, or sponsored links are the ones prominently displayed above or beside the organic search results is a product of SEM.
SEO and SEM are not Competing services. SEO is a subset of SEM Considered services. If you want to conduct business on the Internet you need to be visible in Both organic and advertised links, que means you need both SEO and SEM.