Kali Linux definition
Kali Linux is the world’s most popular offensive-security-optimized Linux distro. Maintained and managed by the fine folks at Offensive Security, Kali was born in 2006 as BackTrack Linux, but after a major refactoring in 2013 got the name Kali. What does the name mean? Well, we’ll get to that.
Kali is free to download and use but is intended as a specialized Linux distro optimized for penetration testing and not as a day-to-day operating system for checking your email or web browsing or sharing cat gifs on the Book of Faces.