How is Ubuntu different from Debian?

So maybe its crazy for me to answer this, having just joined Canonical 3 months ago (today!) and having only run Ubuntu out of curiosity for the few years before joining Canonical. It might even be silly for me to answer it, given that I am on the server team, and Ubuntu definitely has a very large focus on making "Linux for Humans", ergo, the desktop.

To me, the release cycle is everything. Yes there are some things that will never go back to Debian, because these things are somewhat counter to Debian's philosophies. But these are by-products of the greater goal of usability.

When Ubuntu was started, the idea was simple. Debian was awesome then, and is still awesome today. I ran it exclusively for several years and it served me well on laptops, desktops, and especially on servers, being a server kind of guy. But that release cycle was so slow that all of the cool whiz bang stuff that people were producing on Linux was just not making it into the stable releases, and the unstable development release that had all of these things was un-installable (no official isos) and broken quite often.

So by saying "we're going to limit our focus to a couple of architectures, and a subset of packages" (the "main" archive in Ubuntu), the Ubuntu project was able to commit to releasing a tested, stabilized OS with all of that cool new stuff in it. They were also able to commit to carrying a bit of a delta from Debian that was highly focused on usability. By committing capital investment to it, Canonical was able to commit to having the technical staff available to make that happen.

One awesome part of that was that they (I say they, because I am not an Ubuntu member yet) could still keep a lot of the wide breadth of Debian software by creating the "universe" archive. Even better, a community (MOTU) grew up around that to make sure it received some stabilization before release as well.

So, to sum it all up with an analogy.. Ubuntu is to Debian, as your local restaurant is to the local farmer's market. Chef Ubuntu goes to the Debian farmer's market periodically, finds the best fresh ingredients, mixes them with his own special blend, and produces food for his intended audience. For people who enjoy cooking, they can, and do, just go down to the market and get what they need.

Like many popular conceptions, the common characterizations of Debian and Ubuntu are only partially true. Debian’s reputation as an expert's distribution is partly based on its state a decade ago, although it does provide more scope for hands-on management if that is what you want. Similarly, while Ubuntu has always emphasized usability, like any distro, much of its usability comes from the software that it includes — software that is just as much a part of Debian as of Ubuntu.

So what are the differences between these Siamese twins? Looking at installation, the desktop, package management, and community in the two distributions what emerges is not so much major differences as differences of emphasis, and ultimately, of philosophy.

That was a quote from Bruce Byfield who hits the nail on the head. In the comparison between Ubuntu and Debian, the philosophy behind the software is the key difference between the two.

Full article

Ubuntu syncs from Debian every six months (weeks before every releases). Any package that doesn't have any Ubuntu specific changes in Ubuntu (i.e. the previous version was also from Debian) or isn't in Ubuntu already, gets synced into Ubuntu's Universe (free and third-party). MOTU put a lot of work into maintaining the Universe, but this isn't where Ubuntu differs from Debian the most.

Ubuntu's distinctive packages are those in the Main repository (free and Canonical supported). (There is a table of the various repositories on the Ubuntu Team Wiki). This is where Canonical comes into the picture. When you read articles on the cool new things that Ubuntu will have and change in the next release, you're probably reading about something that will arrive in main. This is where Ubuntu is different from Debian.

For me personally the major difference it is actually a a lot about the release cycle. I find it a great benefit that I have the option of going for a kind-of-stable new release every six month, instead of having to choose between a potentially rather old stable release or the constant moving target of the testing release.

Ubuntu is generally based on the "unstable" version (codename "sid") of Debian. They take Debian "unstable" every 6 months and stabilise it. Ubuntu and Debian packages are binary incompatible.