Ethical hacking involves legally accessing computer systems and networks to test security and find vulnerabilities. It helps identify weaknesses that criminals could exploit. There are different types of hackers defined by their intentions and knowledge - white hat hackers help companies, while black hat hackers intend harm. Ethical hacking is important as it helps secure systems from real threats like brute force attacks, buffer overflows, denial of service attacks, and backdoors. Proper security measures include using antivirus software, strong unique passwords, and limiting access to admin accounts.