They are simply pieces (or a piece) of glass inserted in the center part of the cabinet’s door. Glass inserts are highly customizable, so you can easily make yours unique.

Pros	Cons
Will make your kitchen seem larger and brighterMany styles to choose fromVery easy to cleanConvenient to locate your itemsUnique decorative element that looks stunning	Cluttered kitchenware is visible. More so in the case of transparent glass and less for frosted and more opaque optionsFragile, so you need to avoid slamming and any sort of rough behavior when handling themCustom options will be more expensive