From the WareGlossary

Adware: software that displays advertising for other products and/or services (often downloaded from the internet by the software).

From WikiPedia

Adware or advertising-supported software is any computer program or software package in which advertisements or other marketing material are included with or automatically loaded by the software and displayed or played back after installation or in which information about the computer or its users activities is uploaded automatically when the user has not requested it. These applications often present banner ads in pop-up windows or through a bar that appears on a computer screen. read more