Online advertising is a type of mass communication which is based on traditional form of advertising but develops its own communication strategies in correlation with the new technical and medium based requirements. Broadly, online advertising is about delivering advertisements to Internet/online users via Web sites, e-mail, ad-supported software and Internet-enabled smart phones. The biggest advantage over traditional advertisement is it is not limited by geography or time.
Examples of online advertising include contextual ads on search engine results pages, banner ads, Rich Media Ads, Social network advertising, interstitial ads, online classified advertising, advertising networks and e-mail marketing, including e-mail spam.
Anatomy of a a Google SERP (Search Engine Results Page)