SEM is an adjunct SEO. SEM uses ad words depending on the context, SEM can be an umbrella term for various means of marketing a website including SEO, or it may contrast with SEO, focusing on just paid components, pay per call, article submissions, advertising and making sure SEO has been done.
A keyword analysis is performed for both SEO and SEM, but not necessarily at the same time. SEM and SEO both need to be monitored and updated frequently to reflect changing usage.
In some contexts the term SEM is used exclusively to meanPay per click advertising, particularly in the commercial advertising and marketing communities which have a vested interest in this narrow definition. Such usage excludes the wider search marketing community that is engaged in other forms of SEM such as Search Engine Optimization and Search Retargeting.
Another part of SEM is Social Media Marketing (SMM). SMM is a type of marketing that involves exploiting social media to influence consumers that one company’s products and/or services are valuable.
Some of the latest theoretical advances include Search Engine Marketing Management (SEMM). SEMM relates to activities including SEO but focuses on return on investment (ROI) management instead of relevant traffic building (as is the case of mainstream SEO).
SEMM also integrates organic SEO, trying to achieve top ranking without using paid means of achieving top in search engines, and PayPerClick SEO. For example some of the attention is placed on the web page layout design and how content and information is displayed to the website visitor.