Slackware is a free and open source

Free and open source software

Free and open-source software or free/libre/open-source software is software that is liberally licensed to grant users the right to use, study, change, and improve its design through the availability of its source code...

 Linux

Linux

Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...

-based operating system

Operating system

An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...

. It was one of the earliest operating systems to be built on top of the Linux kernel

Linux kernel

The Linux kernel is an operating system kernel used by the Linux family of Unix-like operating systems. It is one of the most prominent examples of free and open source software....

 and is the oldest currently being maintained. Slackware was created by Patrick Volkerding

Patrick Volkerding

Patrick Volkerding is the founder and maintainer of the Slackware Linux distribution. He is the "Slackware Benevolent Dictator for Life." Volkerding earned a Bachelor of Science in computer science from Minnesota State University Moorhead in 1993.For a short while, Chris Lumens and others assisted...

 of Slackware Linux, Inc. in 1993. The current stable version is 13.37, released on April 27, 2011.

Slackware aims for design stability and simplicity, and to be the most "Unix-like

Unix-like

A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification....

" Linux distribution

Linux distribution

A Linux distribution is a member of the family of Unix-like operating systems built on top of the Linux kernel. Such distributions are operating systems including a large collection of software applications such as word processors, spreadsheets, media players, and database applications...

, making as few modifications as possible to software packages from upstream and using plain text files and a small set of shell

Shell (computing)

A shell is a piece of software that provides an interface for users of an operating system which provides access to the services of a kernel. However, the term is also applied very loosely to applications and may include any software that is "built around" a particular component, such as web...

 scripts for configuration and administration.
The name "Slackware" stems from the fact that the distribution started as a private side project with no intended commitment.