Adware is unsolicited commercial software that comes combined with a host application, usually freeware or shareware, which displays advertising while the program is running or through some other triggering mechanism. Some adware hides components and disables removal techniques making it difficult to remove. Adware may also gather user information which causes privacy concerns.
Adware is most often integrated into free applications. MyWay Searchbar, which has utilities such as SmileyCentral and Zwinky, and WeatherBug (adware can be turned off with a paid upgrade) are examples of apps that reported to contain adware. Adware and spyware programs may also be installed because your browser or operating system has a security hole which was exploited.
Pop-up advertisements appear during web browsing or general desktop use. These are annoying and in some cases degrade system performance.