This is a brief section that answers a few questions about the Linux operating system. It is not intended to replace the real documentation about Linux, however.
Linux is a freely-distributable kernel and operating system that works virtually the same as UNIX. Unlike all other available truly UNIX-like operating systems (this means those that provide memory protection and virtual memory), it is built from the ground-up from scratch to comply with open standards. Currently, Linux complies with virtually all of the POSIX.1 standard (the only completely vendor-independent standard), and work is underway to finish work on compliance with the System V Interface Definition (SVID) and other commercially-established standards.
Linux was started in 1991 by Linus Torvalds, who at the time was an undergraduate student in Computer Science at the University of Helsinki in Finland. While Linus is no longer a starving college student (he now works for Transmeta, a highly-secretive Silicon Valley company), he continues to coordinate the work on the kernel and makes significant contributions of his own, particularly on the Alpha and SMP (symmetric multiprocessing) code. The names of many of the other people who have contributed to the Linux kernel can be found in the CREDITS and MAINTAINERS files that are included with the Linux kernel sources.
More of Linux's history (particularly the history of Linux/m68k) is covered in the next section of the FAQ.
The Linux kernel is vaguely equivalent to the Kickstart under AmigaOS. It provides basic services to the operating system, but that's about it. Unlike AmigaOS, it requires at least one other program to launch (a shell [command line interpreter] or a special program called init). Without another program, you'll never even get to a command prompt.
The Linux operating system is a collection of programs (such as interpreters, shells, utilities, applications, and daemons) and libraries that facilitate user interaction with the system. Much of the Linux operating system is derived from the Free Software Foundation's GNU project and the University of California at Berkeley Source Distribution of Unix (BSD). The Linux OS also includes software from other sources, some of which was written specifically for Linux.
For the most part, I use the term Linux as the generic term for both the operating system that most Linux users use and to refer specifically to the kernel. Others would use "GNU/Linux", or a distribution name (e.g. "Red Hat Linux", "Slackware Linux", or "Debian GNU/Linux"), for the operating system, reserving "Linux" strictly for the kernel. Suffice it to say it's not worth the effort to try to convince me to adopt this alternative terminology (you can start the GNU/Linux/m68k FAQ if you like :-).
Where the distinction between one meaning of Linux and another is unclear, I apologize in advance.
MkLinux is a project sponsored by Apple (in collaboration with the Open Group, née the Open Software Foundation) to build a Microkernel-based Linux kernel for PowerPC (and some other) systems.
Linux/m68k is a project to build a monolithic Linux kernel for 680x0 systems. It has no connection with Apple or the OG/OSF (as a matter of fact, Apple, unlike many other manufacturers, has been downright unhelpful with the m68k Linux port).
Unfortunately, the use by some of the term "MacLinux" has added to the confusion and made a lot of people think that MkLinux and Linux/m68k on the Macintosh are the same project. They aren't. Not even close.