A deeply open back between fine straps is the focus of this close rear view. Pale patterning is visible around the lower edge and sides. One arm rests behind the head, making shoulder position part of the effect. The opening is easy to recognise as a design idea. The front, full skirt and ordinary stance with relaxed arms are absent, however. This single perspective cannot establish the support or fit of the complete garment.
If you want this kind of back, show the image as a question about shape rather than proof of a particular product. Try the offered model with your intended underwear. Let your arms hang first, sit down and then compare a greeting movement. Request a rear view in both postures. Ask which strap or back adjustments are possible on the actual dress. A decorated open edge cannot be assessed for alteration from a picture alone. Add a normal side view so your choice does not rely entirely on this especially open framing.