Debian 是一个 GNU/Linux 的发行版。我们稍后将会详细地讨论什么是发行版
第 1.5 节 “发行版的角色”。但是当前情况下，我们暂且将其简单地归纳为一个完整的操作系统，包括软件和系统的安装及管理，所有的这些都基于 Linux 内核和自由软件（尤其是来自 GNU 项目的自由软件）。
当他在自由软件基金会（FSF）的领导下于1993年创建 Debian 时，Ian Murdock 有清晰的目标，他在 Debian Manifesto 中对其作了阐述。他所追求的自由操作系统将有两个首要的特性。第一点是质量：Debian 将在最大的关怀与努力下进行开发，以与 Linux 内核相配。另外，它同样将是一个非商业化的发行版，足够可靠而能够和主流商业发行版相竞争。在他眼里，这两个雄心壮志只能以开放 Debian 开发过程的方式达成，正如 Linux 和 GNU 工程所做的那样。因此，互帮互查将能够持续地改进这个项目。
Debian, remaining true to its initial principles, has had so much success that, today, it has reached a tremendous size. Currently there are 10 hardware architectures officially supported and also other kernels like FreeBSD (although the FreeBSD-based ports are not part of the set of officially supported architectures). Furthermore, with more than 56,000 source packages, the available software can meet almost any need that one could have, whether at home or in the enterprise.
The sheer size of the distribution can be inconvenient: it is really unreasonable to distribute 16 DVD-ROMs to install a complete version on a standard PC… This is why Debian is increasingly considered as a “meta-distribution”, from which one extracts more specific distributions intended for a particular public: Debian Science for scientific use, Debian Edu for education and pedagogical use in an academic environment, Debian Med for medical applications, Debian Jr. for young children, etc. A more complete list of the subprojects can be found in the section dedicated to that purpose, see
第 1.3.3.1 节 “Debian 现有的子计划”.
这些 Debian 的组成部分由定义清晰的框架组织而成，保证“子发行版”之间互相兼容、互不干扰。它们都采用一致的方案释放出新版本。同时它们都基于相同的基础构建而成，可以轻松地使用 Debian 仓库中的软件进行扩展、完善和个性化配置。
所有 Debian 的工具都遵循这个指导方向：debian-cd 已经存在很长时间了，它可以用来创建一组光盘，其中仅包含一系列预先选择的软件包；debian-installer 也是一个模块化的安装工具，易于适应不同的需求。APT 可以使用不同的来源安装软件包，同时保证系统整体的一致性。
Debian follows all of the principles of Free Software, and its new versions are not released until they are ready. Developers do not work upon a set schedule and don't have to rush to meet an arbitrary deadline. People frequently complain of the long time between Debian's stable releases, but this caution ensures that Debian's legendary reliability is met: long months of testing are indeed necessary for the full distribution to receive the “stable” label.
Debian will not compromise on quality: all known critical bugs on key packages are resolved in any new version, even if this requires the initially forecast release date to be pushed back. Optional packages whose critical bugs are not fixed, and thus do not meet the quality requirements, are simply dropped from the stable release.
从法律上来说，Debian 是一个由美国的非营利志愿者协会管理的项目。这个项目大约有一千左右的 Debian 开发者，但是聚集了远超这个数的贡献者（翻译者，bug 报告者，艺术家，临时开发者等）。
To carry its mission to fruition, Debian has a large infrastructure, with many servers connected across the Internet, offered and hosted by many sponsors.
