The support and developers of the GNU program, especially Richard Stallman, refer to a Unix-like operating system called Linux as GNU/Linux.
Linux is not a complete operating system, but a Unix-like kernel. It was developed by Linus Torvalds and others. The first version was released in 1991. The GNU program started in 1984 with the goal of completing a complete Operating System Based on free software. When Linux was released in 1991, the GNU program had completed most of the Software except the operating system kernel, including a shell program, a C-language library, and a C-language compiler. Linus Torvalds and other early Linux developers added these tools in Linux to complete the Linux operating system.
Linux became popular in the middle of 1990s, So Richard Stallman, the creator of the GNU program, asked the Linux operating system to be renamed "GNU/Linux" on the grounds that Linux uses many GNU programs. The free operating system is independent of Debian, which is called Debian GNU/Linux.