X Window System
The X Window System (often called X11 or simply X) is a windowing system that provides a framework for building graphical user interfaces (GUIs) on Unix-like operating systems. It enables networked display capabilities, allowing applications to run on one machine while displaying their output on another. X serves as the foundation for desktop environments like GNOME and KDE, handling input devices, window management, and rendering.
Developers should learn X when working on Linux or Unix-based systems that require GUI applications, remote desktop access, or embedded displays. It is essential for building cross-platform graphical tools, system administration interfaces, or when needing low-level control over display and input in environments where newer alternatives like Wayland are not yet adopted. Use cases include developing desktop applications, remote visualization tools, or maintaining legacy systems in research, engineering, or server environments.