What is the difference between a computer virus and malware?

Every virus is malware, but not every piece of malware is a virus — the same way every square is a rectangle, but not every rectangle is a square.

Common types of malware

• Virus — attaches itself to a host file or program and spreads when that file is shared or run
• Worm — spreads on its own across networks, without needing to attach to a file or wait for a user to run anything
• Trojan — disguises itself as legitimate software to trick users into installing it
• Ransomware — encrypts a victim's files and demands payment for the decryption key
• Spyware — quietly monitors activity and steals information, like keystrokes or credentials
• Adware — floods a device with unwanted advertising, sometimes bundled with legitimate downloads

In everyday conversation people often say "virus" to mean any kind of infection, but from a security standpoint the specific type matters — it determines how the threat spreads and how you remove it.