In application software, it is common for software to be offered in two ways – one as a free, advertising-supported version, and the other a paid, ad-free version. Some software developers offer adware as an alternative to software licenses, funding the development of the software with higher fees for advertisers. Adware is also a popular business model for software as a service (SaaS), with popular examples including Gmail and Facebook.
Adware is often used to describe a type of malware which displays unwanted ads to computer users. Ads produced by malicious adware often display as a pop-up or ‘unclosable’ window.