Windows is a graphical user interface (GUI) that allows users to work with multiple applications and documents simultaneously. It uses icons, menus, and overlapping windows to represent programs, files, and folders. Some key features of Windows include the desktop, start menu, taskbar, control panel, and accessories like Paint and Calculator. Shortcut keys allow efficient navigation and common tasks like copying, cutting, and pasting. The desktop contains icons for common programs and locations, while the start menu provides access to programs, settings, help, and shutdown options.