Ethical Hacking, also known as penetration testing or pen testing, is legally breaking into computers and devices to test an organization's defenses. It's among the most exciting IT jobs any person can be involved in. You are literally getting paid to keep up with the latest technology and get to break into computers without the threat of being arrested.
Companies engage ethical hackers to identify vulnerabilities in their systems. From the penetration tester's point of view, there is no downside: If you hack in past the current defenses, you’ve given the client a chance to close the hole before an attacker discovers it. If you don’t find anything, your client is even happier because they now get to declare their systems “secure enough that even paid hackers couldn’t break into it.”