Although nearly two decades ago, the originator of the term ‘SEM’, intended for SEO to be included in Search Engine Marketing initiatives, that is no longer the case today, and the two terms have separate meanings in the current business world. In the common business language of today, SEM really only includes the paid marketing and advertising aspect of search engine marketing.

For instance, all the ads you pay Google and Bing for are considered to be part of search engine marketing, but not the organic results which appear on a Search Engine Results Page (SERP). Since this is pay-per-click advertising, the most important associated terms are cost per click and cost per acquisition, since they assign dollar values to all those user clicks.

How SEO Differs from SEM

Clearly, the definition of SEM has narrowed over the last two decades and has come to mean strictly the paid part of advertising with search engines. By contrast, Search Engine Optimization is a term that covers all those tactics and strategies which can be used to improve a website’s ranking by the major search engines. Some of these would include liberal use of popular search keywords in the text, including backlinks from other sites, including image tags with photos and graphics, and adding meaningful meta descriptions. These practices are all designed to improve a site’s position in the search rankings but have nothing to do with paid efforts to increase ranking.

That can be considered the primary difference between SEM and SEO – the fact that SEM does involve paid efforts to have an ad appear prominently on a SERP, whereas SEO does not involve payments to the search engines. While the two terms started out being closely related in 2001 when SEM first came into being, there has been a divergence since that time, and they now constitute two entirely different concepts. When you think SEM, think ‘paid advertising‘, and when you think SEO, think ‘organic site improvement’. That should help to keep the two clear in your mind.