Online advertising, also called online marketing or Internet advertising, is a form of marketing and advertising which uses the Internet to deliver promotional marketing messages to consumers. It includes email marketing, search engine marketing (SEM), social media marketing, many types of display advertising (including web banner advertising), and mobile advertising. Like other advertising media, online advertising frequently involves both a publisher, who integrates advertisements into its online content, and an advertiser, who provides the advertisements to be displayed on the publisher's content. Other potential participants include advertising agencies who help generate and place the ad copy, an ad server who technologically delivers the ad and tracks statistics, and advertising affiliates who do independent promotional work for the advertiser. Internet marketing can also be broken down into more specialized areas such as Web marketing, email marketing and social media marketing: 1) Web marketing includes e-commerce Web sites, affiliate marketing Web sites, promotional or informative Web sites, online advertising on search engines, and organic search engine results via search engine optimization (SEO). 2) Email marketing involves both advertising and promotional marketing efforts via e-mail messages to current and prospective customers. 3) Social media marketing involves both advertising and marketing (including viral marketing) efforts via social networking sites like Facebook, Twitter, YouTube and Digg.