What is Hacker?

What is hacker actually?

A Hacker is a person has full knowledge of computer working,and he use knowledge to gain access of another person's computer.

but he uses his knowledge to gain unauthorised access to data so it is called as Hacker. 

What is computer Hacker?

Computer hackers are unauthorized users who break into computer

systems in order to steal, change or destroy information,often by installing dangerous malware without your knowledge or consent. Their clever tactics and detailed technical knowledge help them access information you really don't want them to have.