Kali Linux is mainly used for advanced Penetration Testing and Security Auditing. Kali contains several hundred tools which are geared towards various information security tasks, such as Penetration Testing, Security research, Computer Forensics and Reverse Engineering

Kali Linux OS is used for learning to hack, practicing penetration testing. Not only Kali Linux, installing any operating system is legal.If you are using Kali Linux as a white-hat hacker, it is legal, and using as a black hat hacker is illegal.

Yes, Many hackers use Kali Linux but it is not only OS used by Hackers.Kali Linux is used by hackers because it is a free OS and has over 600 tools for penetration testing and security analytics. Kali follows an open-source model and all the code is available on Git and allowed for tweaking.

Kali Linux contains several hundred tools targeted towards various information security tasks, such as Penetration Testing, Security Research, Computer Forensics and Reverse Engineering. Kali Linux is a multi platform solution, accessible and freely available to information security professionals and hobbyists.

The answer is Yes ,Kali linux is the security distrubtion of linux , used by security professionals for pentesting , as any other OS like Windows , Mac os , It's safe to use .