Debian GNU/Linux is a particular distribution of the Linux operating system, and numerous packages that run on it.
In principle, users could obtain the Linux kernel via the Internet or from elsewhere, and compile it themselves. They could then obtain source code for many applications in the same way, compile the programs, then install them into their systems. For complicated programs, this process can be not only time-consuming but error-prone. To avoid it, users often choose to obtain the operating system and the application packages from one of the Linux distributors. What distinguishes the various Linux distributors are the software, protocols, and practices they use for packaging, installing, and tracking applications packages on users' systems, combined with installation and maintenance tools, documentation, and other services.
Debian GNU/Linux is the result of a volunteer effort to create a free, high-quality Unix-compatible operating system, complete with a suite of applications. The idea of a free Unix-like system originates from the GNU project, and many of the applications that make Debian GNU/Linux so useful were developed by the GNU project.
For Debian, free has the GNUish meaning (see the Debian Free
Software Guidelines). When we speak of free software, we are
referring to freedom, not price. Free software means that you have the freedom
to distribute copies of free software, that you receive source code or can get
it if you want it, that you can change the software or use pieces of it in new
free programs; and that you know you can do these things.
The Debian Project was created by Ian Murdock in 1993, initially under the sponsorship of the Free Software Foundation's GNU project. Today, Debian's developers think of it as a direct descendent of the GNU project.
Debian GNU/Linux is:
mirror sites.
The Debian FTP archives also carry approximately 450 software packages (in the non-free and contrib sections), which are distributable under specific terms included with each package.
Although Debian GNU/Linux itself is free software, it is a base upon which value-added Linux distributions can be built. By providing a reliable, full-featured base system, Debian provides Linux users with increased compatibility, and allows Linux distribution creators to eliminate duplication of effort and focus on the things that make their distribution special. See I am making a special Linux distribution for a "vertical market". Can I use Debian GNU/Linux for the guts of a Linux system and add my own applications on top of it?, Section 13.3 for more information.
In short, Linux is the kernel of a Unix-like operating system. It was originally designed for 386 (and better) PCs; now, ports to other systems, including multi-processor systems, are under development. Linux is written by Linus Torvalds and many computer scientists around the world.
Besides its kernel, a "Linux" system usually has:
http://www.pathname.com/fhs/.
The combination of the Linux kernel, the filesystem, the GNU and FSF utilities, and the other utilities are designed to achieve compliance with the POSIX (IEEE 1003.1) standard; see How source code compatible is Debian with other Unix systems?, Section 3.3.
For more information about Linux, see Michael K. Johnson's INFO-SHEET
and META-FAQ.
The Hurd is a set of servers running on top of the GNU Mach microkernel. Together they build the base for the GNU operating system.
Currently, Debian is only available for Linux, but with Debian GNU/Hurd we have started to offer the Hurd as a development, server and desktop platform, too. However, Debian GNU/Hurd is not officially released yet, and won't be for some time.
Please see http://www.gnu.org/software/hurd/
for more information about the GNU/Hurd in general, and http://www.debian.org/ports/hurd/
for more information about Debian GNU/Hurd.
These key features distinguish Debian from other Linux distributions:
More than 500 volunteer package maintainers are working on over 4200 packages and improving Debian GNU/Linux. The Debian developers contribute to the project not by writing new applications (in most cases), but by packaging existing software according to the standards of the project, by communicating bug reports to upstream developers, and by providing user support. See also additional information on how to become a contributor in How can I become a Debian software developer?, Section 12.1.
The Debian system builds on the ideals of free software first championed by the
Free Software Foundation http://www.gnu.org/ and in particular by
Richard Stallman. FSF's powerful system development tools, utilities, and
applications are also a key part of the Debian system.
The Debian Project is a separate entity from the FSF, however we communicate regularly and cooperate on various projects. The FSF explicitly requested that we call our system "Debian GNU/Linux", and we are happy to comply with that request.
The FSF's long-standing objective is to develop a new operating system called
GNU based on HURD (http://www.gnu.org/software/hurd/hurd.html),
The project name is pronounced Deb'-ian, with a short e, and emphasis on the first syllable. This word is a contraction of the names of Debra and Ian Murdock, who founded the project. (Dictionaries seem to offer some ambiguity in the pronunciation of Ian (!), but Ian prefers ee'-an.)