Adware is a type of software that displays advertisements on a computer or mobile device. It can slow down a device's performance, track user activity, and expose users to unwanted content. There are various synonyms for this term, including a potentially unwanted program (PUP), a browser hijacker, and a malware ad injector. Other terms include spyware, which can collect personal data, and ransomware, which can hold a device or files hostage until a ransom is paid. It is important to protect against these threats by using antivirus software, keeping devices updated, and avoiding suspicious downloads or links.