Is there a name for the close, minimize and restore buttons?
Going all the way back to the Windows 95 evaluators guide, it simply calls these the Window Buttons.
Apple calls them Title Bar Buttons. Note that they're named Close, Minimize and Zoom. These are also the names assigned in the AppleScript accessibility API:
{"close button", "zoom button", "minimize button"}
It seems Microsoft does not give them a name (anymore?), as they're always listed like the following:
An application window includes elements such as a title bar, a menu bar, the window menu (formerly known as the system menu), the minimize button, the maximize button, the restore button, the close button, a sizing border, a client area, a horizontal scroll bar, and a vertical scroll bar. [...]
The buttons in the upper-right corner affect the size and position of the window. When you click the maximize button, the system enlarges the window to the size of the screen and positions the window, so it covers the entire desktop, minus the taskbar. At the same time, the system replaces the maximize button with the restore button. When you click the restore button, the system restores the window to its previous size and position. When you click the minimize button, the system reduces the window to the size of its taskbar button, positions the window over the taskbar button, and displays the taskbar button in its normal state. To restore the application to its previous size and position, click its taskbar button. When you click the close button, the application exits.
The glossary also does not contain a common term for these buttons.
The GNOME folks call them Window Commands (also here):
Different window commands are appropriate to different types of window. See the description of each particular window type for a list of appropriate window commands. These are the possible window commands:
Close
Closes the window. Always draw this as a button on the window border when relevant to the window type.Maximize
Causes the window to use all unused screen space.Minimize
Causes the window to be temporarily hidden. It will continue to appear on the desktop window list.Roll-up/Unroll
Shows only the title bar of the window, as if it has been "rolled up".
"Window state buttons", although that covers more than just those 3.