The Buttons Window is so peculiar and presents so many characteristics that it deserves a treatment of its own.
As with every window header, the first button enables you to set the window type.
Maximise the window, or return to the previous window display size; return to the old screen setting (CTRL-UPARROW).
The optimal view settings for the current window are restored (HOME).
The following six buttons define the Context of the Button window. Depending on which of these buttons is pressed a second group of buttons may appear further right, defining a sub-context.
Logic Context (F4). No subcontexts.
Script Context. No Subcontexts.
Shading Context (F5). Subcontexts are Lamp Buttons, Material Buttons, Texture Buttons (F6), Radiosity Buttons and World Buttons (F8).
Blender selects sub-context smartly. If you are in Shading context with a Mesh Object selected and Material Sub-context, by selecting a Lamp you automatically switch to Lamp Sub-context and vice-versa. Selecting the camera switches to World Sub-context.
Object Context (F7). No subcontexts.
Editing Context (F9). No subcontexts.
Scene Context (F10). Sub-contexts: Rendering; Animation/Playback and Sound Buttons.
The current frame number is displayed as a NumButton in the header.
A Buttons Window is filled with Panels containing Buttons. Panels can be merged together and, in this case, the Panel presents multiple Tabs to select the buttons. Of course Tabs can be carried out of the panel to form new independent Panels.
Panels can be arranged Horizontally or vertically or freely, they can be collapsed to optimize space.
The Buttons Window global facilities are (Mouse clicks in the Buttons Windows but outside of any Panel):
Panels contained in the Buttons Window are moved altogether. If they are placed horizontally in a horizontal window they are panned left-right, if they are placed vertically in a vertical window they are scrolled top-bottom.
Within certain limits, a Buttons Window Panels can be zoomed in/out.
Panels Menu. You can select: Free, Horizontal and Vertical alignment for panels.
The optimal view settings for the current window are restored. If there is only one 3Dwindow in the current Screen, the NumPad commands for the 3DWindow also work in the ButtonsWindow.