Original: A louver ( American English ) or louvre ( British English ) , from the French l'ouvert ; '' the open one '' ) is a window , blind or shutter with horizontal or , less often , vertical slats , that are angled to admit light and air , but to keep out rain , direct sunshine , and noise .
Simplified: A louver ( American English ) or louvre ( British English ) , from the French louvert ; '' the open one '' ) is a window , blind or shutter with horizontal or , less often , vertical slats .