What is different between bugs and virus

Answer 1

VIRUS : A computer virus, much like a flu virus, is designed to spread from host to host and has the ability to replicate itself. Similarly, in the same way that viruses cannot reproduce without a host cell, computer viruses cannot reproduce and spread without programming such as a file or document.

BUG : An error or defect in software or hardware that causes a program to malfunction. Often a bug is caused by conflicts in software when applications try to run in parallel.

Answer 2

Bugs aren't intentional behaviours, virus are.

Answer 3

Technically a virus is just a type of malicious code and by definition it is not a stand-alone program, buy a piece of code which attaches to other programs. But most people (including the ones in comments) use term "virus" meaning malicious code.