Adware

Adware, or advertising-supported software, is any software package that automatically renders advertisements in order to generate revenue for its author. The advertisements may be in the user interface of the software or on a screen presented to the user during the installation process. The functions may be designed to analyze which Internet sites the user visits and to present advertising pertinent to the types of goods or services featured there. The term is sometimes used to refer to software that displays unwanted advertisements known as malware.

In legitimate software, the advertising functions are integrated into or bundled with the program. Adware is usually seen by the developer as a way to recover development costs, and in some cases, it may allow the software to be provided to the user free of charge or at a reduced price. The income derived from presenting advertisements to the user may allow or motivate the developer to continue to develop, maintain and upgrade the software product. The use of advertising-supported software in business is becoming increasingly popular, with a third of IT and business executives in a 2007 survey by McKinsey & Company planning to be using ad-funded software within the following two years. Advertisement-funded software is also one of the business models for open-source software.

Some software is offered in both an advertising-supported mode and a paid, advertisement-free mode. The latter is usually available by an online purchase of a license or registration code for the software that unlocks the mode, or the purchase and download of a separate version of the software.

Some software authors offer advertising-supported versions of their software as an alternative option to business organizations seeking to avoid paying large sums for software licenses, funding the development of the software with higher fees for advertisers.

Examples of advertising-supported software include Adblock Plus ("Acceptable Ads"), the Windows version of the Internet telephony application Skype, and the Amazon Kindle 3 family of e-book readers, which has versions called "Kindle with Special Offers" that display advertisements on the home page and in sleep mode in exchange for substantially lower pricing.

...
Wikipedia