The "Linux" kernel

What is a kernel

A kernel is a computer program at the core of a computer's OS (operating system). It generally has complete control over everything in the system. The kernel performs its tasks, such as running processes, managing hardware devices such as the hard disk.

The "Linux" kernel

April 1991, Linus Torvalds, at the time a 21-year-old computer science student at the University of Helsinki, Finland, started working on some simple ideas for an operating system inspired by UNIX, for a personal computer. On 17 September 1991, Torvalds prepared version 0.01 of Linux. On 5 October 1991, Torvalds announced the first "official" version of Linux, version 0.02. After that, despite the limited functionality of the early versions, Linux rapidly gained developers and users around the world. Then in March of 1994, Linux 1.0.0 was released with 176,250 lines of code. It was the first version suitable for use in production environments. As of 2022 The Linux kernel has around 27.8 million lines of code.

Linux is a free, open source kernel, released under the GNU General Public License (GPL). Anyone can run, study, modify, and redistribute the source code, or even sell copies of their modified code, as long as they do so under the same license. Unlike proprietary software, open source software is computer software that is developed as a public, open collaboration and again is made freely available to the public.

To be clear...Linux is a kernel. It is not a OS. Linux is also known as a monolithic kernel. Another type of kernel is called a hybrid kernel. Hybrid kernels are used in most commercial operating systems such as Microsoft windows 10, 11 and  Apple macOS.