The definition says that a hacker is someone who’s proficient at computers and computer networks.
Shortly, hackers come in three shades:
Whitehat hackers – who are cyber security experts and use their knowledge and skills for good, helping protect companies and individuals;
Greyhat hackers – are right in between, as they use methods which are not entirely ethical, but not necessarily illegal to acquire information which they then sell to third parties;
Blackhat hacker – who are cyber criminals and choose to put their know-how and resources to work for malicious purposes.
Credit: @Daily Security Tip