glutCreateWindow creates a top-level window. The name will be provided to the window system as the window's name. The intent is that the window system will label the window with the name.
Implicitly, the current window is set to the newly created window.
Each created window has a unique associated OpenGL context. State changes to a window's associated OpenGL context can be done immediately after the window is created.
The display state of a window is initially for the window to be shown. But the window's display state is not actually acted upon until glutMainLoop is entered. This means until glutMainLoop is called, rendering to a created window is ineffective because the window can not yet be displayed.
The value returned is a unique small integer identifier for the window. The range of allocated identifiers starts at one. This window identifier can be used when calling glutSetWindow.
The proper X Inter-Client Communication Conventions Manual (ICCCM) top-level properties are established. The WM_COMMAND property that lists the command line used to invoke the GLUT program is only established for the first window created.