I'm reading Wikipedia about X11 and it says that:
In its standard distribution it is a complete, albeit simple, display and interface solution which delivers a standard toolkit and protocol stack for building graphical user interfaces on most Unix-like operating systems...
But later it says that:
X primarily defines protocol and graphics primitives - it deliberately contains no specification for application user-interface design, such as button, menu, or window title-bar styles.
So, does X11 provide widgets like a button or a window panel/frame, etc or not? What is a graphic primitive? What does X11 provide exactly?
It is also stated that:
X does not mandate the user interface; individual client programs handle this. Programs may use X's graphical abilities with no user interface.
What does this mean?