What is Linux?
The name "Linux" is usually used to mean a complete operating system, like Microsoft's Windows or Apple's Mac OS X. But really, deep down, "Linux" is just the bit that looks after your computer: it runs programs, it stores information in your RAM and on your hard disk, and it also provides support for things like connecting to a network.
Linux by itself, known as "the kernel" because it's the true core of any desktop system, isn't very interesting. It doesn't have a graphical user interface. It doesn't let you chat to your friends online. And it certainly won't open any Microsoft Office documents! Instead, all these services are provided by applications that are designed to run on top of Linux.
Because just giving someone the Linux kernel is pretty much useless, a lot of people have taken the time to put it together with lots of other programs, utilities, tools and documentation to produce something that is useful. These combinations of software is called a Linux distribution (usually shortened to "distro"), and, because people choose different kinds of software or target different kinds users, there are lots of different distros around.
Who created Linux?
Linux was created in 1991 as the personal project of a Finnish student called Linus Torvalds, and since then it has grown quickly as other people (and, later, companies) joined in its development. Linux was originally written to work only on Intel CPUs, but since then has been made to work on dozens of different computer architectures - many phones run Linux, for example.
Why is Linux free?
Nearly all the Linux distributions in the world are free, meaning that they cost $0 to install and use on your computer. The reason for this is that all Linux distros take their software from the same pool - if one distro has a really awesome program, chances are 50 other distros also have exactly the same feature, so if a company tried to sell their version of Linux people would just go elsewhere.
The big upside to all this is that if you ever decide you don't like the direction one distro is taking, you can jump ship and try a different one - you'll find all the same software there ready for you.
What's the difference between free software and open source?
The term Free Software was coined to mean software that came with freedoms that you otherwise would not have had. For example, if a program is Free Software it means you can download its source code, modify it, sell it and all sorts of other good things. But, a Free Software application doesn't necessarily have to have zero cost. This is where a lot of people get confused, so the most common explanation is "free as in speech, not as in beer."
If you're completely lost now, let us explain. You have free speech in this world. That doesn't mean you pay $0 for the right to talk, instead it means that you have the freedom to say what you want. Conversely, if I give you a free can of beer, that beer does have zero cost - the beer doesn't have any freedoms to express its opinion! So when people say Free Software they mean "free" as in "freedom", not "free" as in "cost". Yes, most Free Software does cost nothing, but it's not required.
Because of this mixup between free speech and free beer, another group of people came up with the term "open source". This was originally meant to have the same meaning - that someone could download the source code to a program and do what they want with it - but a lot of people have since misinterpreted that too!
For most people, Free Software and Open Source mean exactly the same thing. Open source has slightly looser restrictions in its definition, which means that a Free Software program is also open source, but an open source program is not necessarily Free Software.
Why is Linux open source?
One of Linux's many advantages is that it is developed by thousands of programmers around the world. Intel, IBM, Oracle, Google, HP, AMD, Nvidia, Dell, Cisco, Nokia, Motorola and more all help contribute to Linux precisely because it is open. Intel wants its CPUs, its graphics chips and its network cards to work perfectly on Linux, so it writes the programming code itself and gives it away as part of Linux. As a result, you can be sure you're getting the fastest and most stable experience around!
The other advantage to Linux being open is that no one vendor can control it - no one can pull it one direction, because everyone works together.
What is the GPL?
GPL stands for "General Public License", and is a software licence that lets people download, modify and distribute the source code to a program. The GPL is the most common licence used on Linux, which is why you get all the software at no cost and also why you can install it on as many machines as you want. There are lots of other licences in use, but the GPL is by far the most popular.
Why is Linux different?
One of the big advantages to Linux is its openness. If you choose one distro and find it doesn't suit you in the future, you're not stuck with it. Or if the developers behind it try to make changes that no one else likes, the users can go somewhere else to get their software - it's all shared! This is very different to the traditional software model used by both Microsoft and Apple where they (and only they!) can provide upgrades to their operating system, and if you find the latest version of Windows runs slowly there's not much you can do!
What is The Linux Foundation?
The Linux Foundation is a nonprofit consortium dedicated to fostering the growth of Linux. Founded in 2000, it sponsors the work of Linux creator Linus Torvalds and is supported by leading companies and developers from around the world. The Linux Foundation promotes, protects and advances Linux by providing unified resources and services needed for open source to successfully compete with closed platforms.
Why do you call it GNU/Linux and not Linux?
Most operating system distributions based on Linux as kernel are basically modified versions of the GNU operating system. We began developing GNU in 1984, years before Linus Torvalds started to write his kernel. Our goal was to develop a complete free operating system. Of course, we did not develop all the parts ourselves—but we led the way. We developed most of the central components, forming the largest single contribution to the whole system. The basic vision was ours too.