Kali Linux is a Linux distribution for testing security and hacking. This distribution is made by the team backtracks backtracks contrary was based on Ubuntu, based on Debian Kali. It is not supported by the team backtracks project and Kali has been replaced.
BackTrack is in fact the previous version Kali, one of the distribution of open source (open source) Linux that aims to help more Mac security professionals network / IT to perform penetration testing and the discovery of weaknesses in the design for users collection of security tools provides the professional and powerful.
There are several ways to use Kali Linux, it can be installed on the hard disk, virtual machines running on the Live CD or Live USB boot off or not. 
Tests immense influence on the operating system, such as Wireshark (analysis of packet), nmap (a searcher Perth), John the Ripper (password cracking), Aircrack-ng (penetration testing on network and local) have been completed and All of them successfully finished.

A key feature of the software Kali Linux:
- Full customization of the ISO file and the Mac that created a custom image of Kali Linux
- High flexibility in defining features and the ability to create self installing, reverse VPN auto-connecting and network bridging Kali image
- Installation of the USB
- Encrypted with LUKS Full Disk Encryption or FDE
- Automated deployment of operating system Kali
- Mastering Pro Tools package meta Linux Kali Kali (Kali Metapackages)
- EFI boot support
- Provided as a Live DVD with a run from the DVD or installed on the hard drive
- Run through the virtual machine
- Applicable to all organizations, institutions and IT companies
- Usable for all people with any level of expertise in the field of IT security
- Test the permeability and Security
- A complete and updated set of security tools
- And ...