You can 100% create your own kernel for an operating system, and call it Steve

Linux is the kernel; that is, the core of the operating system, which handles memory, hardware, inputs... Every OS has one. Windows' is called NT, macOS' is called Darwin.

You don't use the kernel, you use the OS. Linux is special because there several operating systems based on Linux; they are called distributions, and they are what you want to use.

You can create your own Linux distribution, by bundling various software packages with the kernel, in a way that caters to specific needs or follows a philosophy (for example, Linux Mint is a distribution focused on ease of use, Archlinux on minimalism..). This is not possible with Windows because their kernel is not licensed under terms which would allow this. It is with Darwin, but unusual.

You can also create your own kernel but this is extremely hard. Getting the computer to boot is easy enough (relatively speaking), but getting programs to run and things to display is much harder. Getting your custom kernel to a usable state is orders of magnitude harder, as it needs to work on and communicate with modern hardware and networks. Linux took more than 30 years of development by thousands of developers (some of them highly talented in a very narrow field of computing) to get to the level it's at.

"Linux" has two meanings. One of them is the kernel itself; another is a collection of operating systems, that Stallman would call "GNU plus Linux" instead.

The later involves two factors. A "hard" one is the presence of the Linux kernel; but there's also two softer and fuzzier ones:

• the operating system behaves like other OSes that the user calls "Linux". For example you're expected to have a /home/username, you can install a different DE/WM if you want, this kind of stuff.
• the OS is open in letter and in spirit. This is ideological but ideology is damn important when dealing with Linux.

A good example of both is ChromeOS: people don't usually call it "Linux", even if it uses the Linux kernel. It's simply too atypical in behaviour, and ideologically too distant from the open source movement.

I'd just like to interject for a moment. What you're refering to as Linux, is in fact, GNU/Linux, or as I've recently taken to calling it, GNU plus Linux. Linux is not an operating system unto itself, but rather another free component of a fully functioning GNU system made useful by the GNU corelibs, shell utilities and vital system components comprising a full OS as defined by POSIX.

Many computer users run a modified version of the GNU system every day, without realizing it. Through a peculiar turn of events, the version of GNU which is widely used today is often called Linux, and many of its users are not aware that it is basically the GNU system, developed by the GNU Project.

There really is a Linux, and these people are using it, but it is just a part of the system they use. Linux is the kernel: the program in the system that allocates the machine's resources to the other programs that you run. The kernel is an essential part of an operating system, but useless by itself; it can only function in the context of a complete operating system. Linux is normally used in combination with the GNU operating system: the whole system is basically GNU with Linux added, or GNU/Linux. All the so-called Linux distributions are really distributions of GNU/Linux!

Linux is a combination of the Linux kernel (some really low level software that tells the OS how to communicate with your hardware, not something most users should worry about) and software from GNU (some Linux users call it GNU/Linux for this reason). This is then used as the base for distros, which are basically just that plus a package manager (how you install apps) and usually a desktop environment and default apps as well.

Theoretically yes, you could create an operating system and name it Steve, but it wouldn't be Linux unless it had the Linux kernel and GNU software.

Edit: as others have pointed out, yes, you can technically have linux distros without GNU, but GNU-based Linux distros are by far the most popular option, so you're highly unlikely to find a distro without GNU unless you're hunting for one.

Linux kernel + everything else you need to make a function os + a mostly free and open approach to software = Linux

The kernel. It's why the BSD distros for example, while very similar to Linux, aren't "Linux".

Strictly speaking, Linux is a free, open-source OS kernel originally developed by Linus Torvalds in 1991. (Linus Torvalds still oversees the kernel's development, but many people now contribute to it.) The Linux kernel needs to be combined with other software to make a working operating system, and that's what Linux distributions (distros) are. Some of the core software with which the Linux kernel is combined comes from the GNU project, which started before the Linux kernel existed, and had the goal of developing a complete free Unix-like operating system. GNU can be used with other kernels but in practice it is almost always used with the Linux kernel.

What we commonly call Linux is the Linux kernel + GNU + other bundled software to make a complete usable operating system. Importantly, this usually includes a package manager to help with installing, updating and removing software, and it often also includes a windowing system and desktop (though it doesn't have to). There are many, many ways of putting this package together, hence there are many Linux distros.

Many Linux distros prioritize free, open-source software (FOSS). Some include only FOSS while others include non-free software too.

Linux is a platform that allows you the freedom to acquire the perfect OS for your needs; Linux Mint for your elderly mother, ChimeraOS for the Steam Deck of your son, Debian for your server, Ubuntu on your laptop you use for work and we can't forget your fully customized Arch/Gentoo on your self-built PC that has been optimized to perfection for your workflow. Whatever problem/use-case/need you might have for your device, Linux offers solutions that are quite possibly the best there is; your mileage may vary depending on your knowledge and experience*.

Linus.

There are other OSes that aren’t mac, windows, or linux. Look at TempleOS for an example

The most important part of Linux is the distribution that provides a boot loader and wraps the Linux kernel in tools & tool management.

What makes Linux particularly special is you can create Steve from a derivative of the Linux kernel. So get cracking!

Apart from being open source what is Linux?

The codebase in git.kernel.org's torvalds/linux.git

Could I not create my own operating system that is different to windows or Macos and call it Steve

Of course, in fact many people have done so: TempleOS, MINIX, SerenityOS, etc.

Mr. Stallman would be angry if you didn't define it as the Linux kernel plus the GNU stuff that you need to do things with the kernel.

Kernel + environment = OS

"Linux" is the name of the OS kernel — the component that manages hardware drivers, schedules processes, provides basic networking operations, and so on. The project that builds that particular kernel was started in 1991 by Linus Torvalds.

However, that kernel is almost always used with an assortment of libraries, utilities, and user-interfaces (such as the bash shell) which are often expected to be part of a "Linux system". Many of these come from the GNU project, which began separately from the Linux kernel as an effort to make a free Unix clone.

When the libraries etc. are the ones from the GNU project — e.g. the C library glibc — we can call the system "GNU/Linux" which is a term used by Debian and some other software distributions.

The awesome sauce, of course!