Windows come in all shapes and sizes. Here is a handy guide to all types of windows. Our most frequently asked question is “What is a french window?” In the professional window cleaning world a french window has grids attached to outside of the glass, whether it be interior or exterior. Most newer replacement windows are dual-paned with any grids in between the two panes of glass. But some newer dual-paned windows also have french grids attached to the outside of the glass.