The practice of marketing websites includes many acronyms which may be confusing to distinguish between. A few of these acronyms are SEF, SEO, and SEM.
A Search Engine Friendly (SEF) website is easily viewable in its entirety by search engines. Once a website is indexed by a search engine, Search Engine Optimization (SEO) then attempts to increase a website's rank relative to its peers within a search engine's organic (non-paid) search results. Search Engine Marketing (SEM) influences a website's position within the paid results area of search engines.
Although the original use of SEM included SEO as a subset activity, lately these terms have become separate and equal, differentiated by money paid to search engines (SEM), and focusing on organic search results (SEO).