This information was taken from the Linux.org website

Debian GNU/Linux is a free distribution of the Linux based operating system. It is maintained and updated through the work of many users who volunteer their time and effort. Along with its large selection of prepackaged software is contains advanced package management tools that allow for easy installation and maintenance on individual systems and workstation clusters. Extensive pre-release testing is done to ensure the highest degree of reliability possible, and a publicly accessible bug tracking system provides an easy way to monitor customer feedback.
The November 2000 issue of LINUX Magazine feautures an article on Debian GNU/Linux 2.2.

Debian Started out as the Free Software Foundation's (FSF) official distribution of Linux. However how Debian has become its own entity and has broken away from FSF. Debian are so devoted to GPL software that they only allow "pure" GPL software to be included in their distribution. Their meaning of pure is that the software is completly open source and that no profit is made from the software.

Most distributions use the RPM (Red Hat package manager) which is similar to the add new software part of control panel in windows. Debian has its own package manager, dpkg. Debian Linux is also able to run on Sun Sparc stations, Strong arm and Alpha's.

Debian is one of the most stable distributions but is also regarded as a more 'Technical' distribution for the advanced user. I can't comment on this as I have never used it, however it seems to get good reviews on all the sites I've visited.

You can find more information at the Debian home pages