What's the part maked 'this' called?

The skirt (that part of the upholstery of a chair or sofa that covers the legs) or flounce (a flounce is pleated or gathered skirt.)

Thanks very much. Does skirt refer to only the clothes, covering the area? Assuming there's a panel underneath the clothes, would you still refer to the area as skirt? Eg, would you say : The skirt of the carriage seat felt hard against his legs ?

AnonymousDoes skirt refer to only the clothes, covering the area?

The skirt or flounce is the fabric. If there is solid wood underneath, it is generally called a panel. I don't know if there is a specific name for that part. The place may even be empty, which allows storage underneath the seat.