These are windows that are used purely to let light in and provide a view but do not need to be opened or operated because there are no ventilation possibilities. You can also choose double glazing windows of the fixed variety if you are located in noisy or traffic prone areas and require better sound proofing.
Two windows of the same type or different types can be combined to produce combination windows. These are usually combinations of fixed windows with casement windows or sliding windows. If more light is required but there is only a limited amount of operating space available for windows, combination windows are the ideal solution