What is a type of window frame called with lots of squares black panes separating the glass?

A type of window frame with multiple squares or panes separated by black muntins is commonly referred to as a "grid" or "muntin" window. This style is often seen in traditional and colonial architecture, giving the window a classic appearance. The individual panes can be either true divided lights (separate pieces of glass) or simulated divided lights (single panes with muntin grids applied).