Thanks to Jeff Alami for
this link.
“Technically speaking, Linux is not an operating system. It is
simply the kernel, or heart, of the operating system. This kernel
handles system processes, hardware access, and many other critical
tasks. The operating system we term “Linux” is in fact a Unix-like
system incorporating the Linux kernel, GNU compiler and utilities,
BSD software, the X Window System for windowing and graphics, and
applications software. A Linux system, in its complete glory, is
sometimes termed “GNU/Linux” because of its reliance on system
software developed by the Free Software Foundation’s GNU
project.”