You might already know that there is not only one but hundreds of different Linux based operating systems. If you wish to have a general introduction and relevant information about the most popular and mainstream GNU/Linux distributions keep reading, this article is for you.
If you want to read about cool distributions that are not so popular (but nevertheless awesome!) you might like to read our list of "Surprisingly cool GNU/Linux distros".
If you wish to dig deeper and understand the concept of distros and the relationship between them, check our post about "What are GNU/Linux "distributions"? (and how to choose the right distro for you)"
Debian is one of the oldest GNU/Linux distros available. The creation of Debian is among the most incredible stories of dreams becoming a reality. The success of Debian is a living proof that Free Software, and generally speaking, cooperation, is viable and very powerful. It started as most Free Software projects: one man (Ian Murdock) had a vision and invited whoever would like to join. Debian soon became a major player that inspired dozens of derivative distributions. It is a massive collaborative work made by a community of developers for the sake of building a good and free operating system.
The difficulty of using Debian is that it requires more effort to install and configure compared to other mainstream distributions. Given its popularity, it's maybe, in part, responsible for spreading the idea that GNU/Linux is made only for experts. There is work done by the Debian community to revert the situation and, everyday, new tools are created to help make Debian easy and user-friendly.
Ubuntu has been among the most popular distribution since its creation in 2004. It was created by a notable contributor of Debian, the South African Mark Shuttleworth. Mark made a fortune with an Internet security company he created (Thawte) and sold for about 500 million dollars. He made lots of things with his money, including a trip to space (!) and the creation of Canonical Ltd., the company behind Ubuntu. He gave ten million dollars from his pocket as a security fund to guarantee the continuity of the operating system. He no longer is CEO of Canonical Ltd. but still has a strong presence in the community. Canonical Ltd. goal is to give everybody access to a good operating system regardless of financial situation, language or disability. For this reason Canonical Ltd. will always provide Ubuntu free of charge, in several languages and with accessibility built-in.
Linux Mint rapidly gained popularity for being a beautiful and easy-to-use distribution. It is for the most part based on Ubuntu/Debian but has been so successful that has started developing its own way of doing things. The decision of Ubuntu to move from GNOME to Unity also motivated many upset Ubuntu users to switch over to Mint, increasing even more its popularity. But in the end, the real reason for Mint's success is that developers are always listening to users feedback and usually release fixes and improvements rather quickly. The focus on user friendliness and usability led Mint to include proprietary drivers and software out-of-the-box (instead of letting the user do that), although they prefer to use Free Software when possible.
Fedora is another heavyweight distro with many loyal hard-core Linux users all over the world. Although it might not be the first choice for newbies it is still a rather easy to install and easy to use distro. Fedora is a community driven distro that is the basis upon which RHEL (Red Hat Enterprise Linux) is built. RHEL is the most successful commercial GNU/Linux distribution around. Red Hat Inc. commercial success is maybe the best example of the financial viability of Free and Open Source Software. If you wish to take a look at RHEL without having to pay, you can download CentOS, an unofficial clone that works just as well.
OpenSUSE is similar to Fedora in the sense that it is a community edition of a commercial GNU/Linux OS (SUSE Linux Enterprise). SUSE is provided by Novell, one of the well established and renowned companies offering a wide range of solutions for GNU/Linux platforms. SUSE is particularly well known for being very reliable and for offering good compatibility with Microsoft products. So much so that Novell's relationship with Microsoft became somewhat controversial at some point.
Slackware is the oldest GNU/Linux distribution still maintained and carries the legacy of a “UNIX feel” system. Slackware is made for people with some UNIX knowledge and preference for working on the command line rather than for people that prefers to work on a graphical user interface. It was initially developed for a University project by Patrick Volkerding and received so many positive feedback that it ultimately became a major distribution.
Arch Linux has many interesting things that differentiate it from the huge number of other distros. It is made for advanced GNU/Linux users that want control over every aspect of his/her OS. To set up Arch you need to know what you want your desktop to look like and what you want to install in it because there are no options by 'default'. Another important aspect of Arch is that it's one of the few "rolling release" distros. This means that you don't have to upgrade your system... ever. Updates keep pouring in all the time, providing always the most recent software available. Although rolling releases are not as stable as scheduled releases, many users consider the advantages of continual updates to be one of the greatest features of Arch.
Gentoo Linux is known for its package management “Portage” and the particularity of being compiled entirely in the user's computer during installation. Some say that compiling the software to fit the computer's configurations provide speed improvements but not all agree that the improvements compensate the hassle and time spent to compile it. In any case, Gentoo aims to be the optimal distribution for every computer, made for users with computing knowledge and some spare time in their hands.
Have I forgotten to include your favourite distro? Drop a comment to express your satisfaction or your outrage and we'll see how the list evolves!