Search engine marketing encompasses a range of activities all centred around making your website more visible when someone uses a search engine. SEM is the process of gaining traffic by purchasing ads on search engines. It is also called paid search and sometimes referred to as CPC (cost-per-click) or PPC (pay-per-click) marketing, because most search ads are sold on a CPC / PPC basis. SEM is short for “search engine marketing,” which once was used as an umbrella term to encompass both SEO (search engine optimization) and paid search activities. However, over time, many adopted the SEM acronym to refer solely to paid search.