Malware is one kind of harmful software.They are

Macro virus: Written in macro languages ,platform independent.They can be embedded with documents.They can be run automatically when a document (word document,excel) is opened or vbs script is run.

Stealth virus: They are written to trick antivirus software by intercepting its request to operating system and providing false information. It hides the modification it makes.

Polymorphic virus: Its hard to detect using signature as it has no parts those are identical.

Self garbling virus: It hides itself from antivirus program by modifing its code . So detection using signature is not effective for this kind of virus

Worms: It has ability to spread from one machine to another.

Bots and zombies: Collection of hacked devices under a command and control of a hacker get compromised and becomes a part of Bot network .

Frimware rootkit: Worst of all malware. It can be hidden within the harddrive frimware chip,so formatting or reinstalling operating system doesn’t remove the virus.

Torjan horse: It acts like a software but runs hidden tasks in background that harm you and your privacy

keylogger: They log your keystrokes.

Rat(remote access tools): It helps to access your system remotely and control your computer.

Ransomware: It encryptes all your private data and tell you to buy the decryption key using crypto currency.

Malvertisement: Online advertisement that downloads malware.

Drive-by-attack: Effects by simply visiting website that contains code to exploit machine