Adware
Adware is a well-known type of malware. Many systems are actively infected with this type of malware from the various installations and other activities they perform. When this type of software is deployed onto a victim’s system, it displays ads, pop-ups, and nag screens, and may even change the start page of the browser.
Typically, this type of software is spread either through a download with other software or when the victim visits a website that deploys it stealthily onto their system.