Because sliding doors and french doors operate.
French doors or sliders.
French patio doors can be considered a little more energy efficient as the central glass panels can be smaller by being set into wider frames whereas sliding doors are almost exclusively created from glazed panels.
Sliding doors overlap which is a more efficient design and creates a tighter seal where as french doors come together with no overlap and an increased chance for air infiltration.
They are unique in that you can open them inwardly or outwardly.
French doors have a wider door frame.
A french style sliding door has the appearance of traditional swing french doors with wider stiles and rails while functioning as a sliding glass door.
Design differences between french patio doors and sliding patio doors.
Milgard french sliding doors combine space saving convenience with the elegance of a french patio door.
A sliding glass door frame is typically narrower than a french patio door.
French patio doors are also known as hinged patio doors or swinging patio doors.
They consist of two doors that open from the center.
Traditional sliding glass doors have two panels with one that slides along rollers to cover the other.
French patio doors are mostly made of glass and look similar to windows.
French doors and sliding doors have different hardware.
A classic model has two side by side panels that swing in or out from hinges on the sides of the frame.