The pleats create the curvature of the sides.
Probably the front of the skirt.
And this is, most likely, the back.
An Altered Skirt
The sides of the skirt are created using pleats in order to achieve the intended curvature. The skirt originally had openings at the sides, decorated with lace. At a later date, the opening has been altered and a slit created. It is now uncertain what side of the skirt was at the front.