What kali linux is ???

Kali is a Linux based operating system developed by Offensive security.Previous version of Kali was BackTrack.
BackTrack had three versions namely BackTrack R1,BackTrack R2 and BackTrack R3. After BackTrack R3,Kali was developed.
So whats the difference between Kali Linux and other linux based operating systems.
Kali is specially designed for hackers.Not exactly for hackers but for pentesters.Penetration testing is a way of finding bugs in network or site in
authorized way.Kali is preloaded with each and every tool which a hacker needs for an attack.