Radio

Radio advertisements are broadcast as radio waves to the air from a transmitter to an antenna and a thus to a receiving device. Airtime is purchased from a station or network in exchange for airing the commercials. While radio has the limitation of being restricted to sound, proponents of radio advertising often cite this as an advantage. Radio is an expanding medium that can be found on air, and also online. According to Arbitron, radio has approximately 241.6 million weekly listeners, or more than 93 percent of the U.S. population.

Online

Online advertising is a form of promotion that uses the Internet and World Wide Web for the expressed purpose of delivering marketing messages to attract customers. Online ads are delivered by an ad server. Examples of online advertising include contextual ads that appear on search engine results pages, banner ads, in pay per click text ads, rich media ads, Social network advertising, online classified advertising, advertising networks and e-mail marketing, including e-mail spam.

A newer form of online advertising is Native Ads; they go in a website's news feed and are supposed to improve user experience by being less intrusive. However, some people argue this practice is deceptive.