1. Software that is free of charge to the user but makes money for its creator by displaying advertisements. Many websites are adware.
2. Software that displays unwanted advertisements on the user’s computer screen. Often concealed in downloaded web pages, it installs itself surreptitiously, either by exploiting security weaknesses or by tricking the user into giving consent, and is often difficult to remove. Adware is regarded as malware and may include an element of spyware.