A pelmet (also called a "cornice board") is a framework placed above a window, used to conceal curtain fixtures.
These can be used decoratively (to hide the curtain rod) and help insulate the window by preventing convection currents.
Exterior timber pelmets are a feature of some historic buildings, fitted on the outside of a window.
These may be purely decorative, or serve to conceal an external blind mechanism.
Due to the appearance of a pelmet, the term is often used to describe an extremely short skirt.