Search engine marketing, or SEM, is a form of Internet marketing that seeks to promote websites by increasing their visibility in search engine result pages (SERPs) through the use of paid placement, contextual advertising, and paid inclusion. The industry peak body Search Engine Marketing Professional Organization (SEMPO), includes search engine optimization (SEO) within its reporting, and SEO is also included in the industry definitions of SEM by Forrester Research, eMarketer, Search Engine Watch, and industry expert Danny Sullivan. The New York Times defines SEM as 'the practice of buying paid search listings'.

Enterprise Search Marketing, also known as Enterprise Search Engine Marketing, is a subset of Search Engine Marketing (SEM) that relates specifically to the implementation, management and measurement of SEM programs at scale–across a variety of business units, geographies, budgets, local languages, search engines and target audiences. As with Search Engine Marketing, there are three main methods: Search Engine Optimization (SEO), paid search engine advertising or pay per click advertising and paid inclusion.

There are several differences between SEM and Enterprise Search Engine Marketing (ESEM), one being the requirement for enterprise-class SEM tools and SEM software solutions to enable organic optimization, search campaign management and ROI analysis at scale. Second, the increased need for well-documented business process, communication and coordination across diverse and disparate teams and stakeholders. Third, a unified education plan to ensure consistent and ongoing application of search best practices at the enterprise level.