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. Examples of online advertising include contextual ads on search engine results pages, banner ads, Rich Media Ads, Social network advertising, online classified advertising, advertising networks and e-mail marketing, including e-mail spam.

Competitive advantage over traditional advertising

One major benefit of online advertising is the immediate publishing of information and content that is not limited by geography or time. To that end, the emerging area of interactive advertising presents fresh challenges for advertisers who have hitherto adopted an interruptive strategy.

Another benefit is the efficiency of advertiser's investment. Online advertising allows for the customization of advertisements, including content and posted websites. For example, AdWords and AdSense enable ads shown on relevant webpages or aside of search results of pre-chosen keywords. Another is the payment method. Whatever purchasing variation is selected, the payment is usually relative with audiences' response.

Purchasing variations

The three most common ways in which online advertising is purchased are CPM, CPC, and CPA.

• CPM (Cost Per Impression) is where advertisers pay for exposure of their message to a specific audience. CPM costs are priced per thousand impressions, or loads of an advertisement. However, some impressions may not be counted, such as a reload or internal user action. The M in the acronym is the Roman numeral for one thousand.

• CPV (Cost Per Visitor) or (Cost per View in the case of Pop Ups and Unders) is where advertisers pay for the delivery of a Targeted Visitor to the advertisers website.

• CPC (Cost Per Click) is also known as Pay per click (PPC). Advertisers pay each time a user clicks on their listing and is redirected to their website. They do not actually pay for the listing, but only when the listing is clicked on. This system allows advertising specialists to refine searches and gain information about their market. Under the Pay per click pricing system, advertisers pay for the right to be listed under a series of target rich words that direct relevant traffic to their website, and pay only when someone clicks on their listing which links directly to their website. CPC differs from CPV in that each click is paid for regardless of whether the user makes it to the target site.

• CPA (Cost Per Action) or (Cost Per Acquisition) advertising is performance based and is common in the affiliate marketing sector of the business. In this payment scheme, the publisher takes all the risk of running the ad, and the advertiser pays only for the amount of users who complete a transaction, such as a purchase or sign-up. This is the best type of rate to pay for banner advertisements and the worst type of rate to charge. Similarly, CPL (Cost Per Lead) advertising is identical to CPA advertising and is based on the user completing a form, registering for a newsletter or some other action that the merchant feels will lead to a sale. Also common, CPO (Cost Per Order) advertising is based on each time an order is transacted.