Viruses and malware are terms for threats that damage devices, steal information, or otherwise inconvenience the user. Viruses take the form of malicious self-replicating software, while malware is a more general term that covers any software designed to cause harm. There are many types of malware and viruses that fall into different categories and act in different ways to accomplish various malicious objectives. For victims of malware and viruses, this can mean anything from being bombarded with ads to having critical financial and personal information stolen.
Ultimately, viruses and malware are digital traps laid by criminals to make money or frustrate others. They take many forms, and all of them are bad.