what is computer virus???

A computer virus is a computer program that can replicate itself and spread from one computer to another. The term "virus" is also commonly, but erroneously used, to refer to other types of malware, including but not limited to adware and spyware programs that do not have a reproductive ability.
Viruses can increase their chances of spreading to other computers by infecting files on a network file system or a file system that is accessed by other computers.
   the types of virus on your computer ;

a. Worm 

Worm is a security flaw or weakness in the computer between us that allows your computer is infected with the virus without having to execution of a file that generally occur in the network.
b. Trojan
Trojan is a program that allows our computer controlled and others through a network or internet.
c. spyware
Spyware is an application that leaked the information data or user behavior in the habit of using computers to outside parties without we realize. Normally used by the advertisers.