LinuxPapers.org: Kernel Basics

The kernel is so important that, in some environments - particularly academic ones - the study of operating systems is limited to the kernel. Linux, which is known to everybody as a set of programs and interfaces, was actually born as a "single" kernel. The founder of the Free Software Foundation and the reputed father of the GNU project, Richard Stallman, stresses that the system known as Linux should more properly be called GNU/Linux.