An Operating System ( OS ) is the software that directly manages a system's hardware and resources, like CPU, memory and storage. The OS sits between applications and hardware and makes the connections between all of your software and the physical resources that do the work. Think about an OS like a car engine. An engine can run on its own, but it becomes a functional car when it's connected with a transmission, axies and wheels. Without the engine running properly, the rest of the car won't work.
Kali Linux is an open source project that is maintained and founded by Offensive Security, a provider of world–class information security training and penetration testing services. In addition to kali linux, offensive security also maintains exploit database.
It is based on debian OS, and have lot of inbuilt tools for penetration testing ( hacking ), it is user friendly and uses gnome desktop environment.
Backbox is an ubuntu based penetration testing linux distribution. It provides penetration test and security assessment oriented providing a network and informatics systens analysis toolkit along with a complete set of other tools required for ethical hacking and security testing.
It is also an debian based operating system used for penetration testing, it is best for disk usage and can run under low configuration systems.
Live Hacking OS is a linux distribution packed with tools and utilities for ethical hacking, penetration testing and countermeasure verification. It includes the graphical user interface GNOME inbuilt. There is a second variation available that has command line only, and it requires very fewer hardware requirements.
Stands for Digital Evidence & Forensic Toolkit and it's an open source distribution of linux built around the DART ( Digital Advanced Response Toolkit ) software and based on the ubuntu Operating System. It has been designed from the ground up to offer some of the best open source computer forensics and incident response tools that can be used by individuals, IT auditors, investigators, militatry, and police.
There are so many Operating Systems used for Hacking we mentioning few of them only.