Linux is an open-source, Unix-like operating system kernel that serves as the foundation for various Linux distributions, which are complete operating systems built around the Linux kernel. Linux was developed in 1991 by Linus Torvalds and has since become one of the most popular operating systems in the world, powering a wide range of devices from servers and desktop computers to embedded systems and mobile devices.

One of the defining characteristics of Linux is its open-source nature. The source code of the Linux kernel is freely available, allowing individuals and organizations to modify, customize, and distribute it according to their needs. This open nature has fostered a vibrant community of developers who contribute to its ongoing development and create numerous software applications and tools that run on Linux.