An off-shoulder band runs around the upper arms of this dress below a shaped front neckline. A pale skirt falls outward from the waist and reaches the floor. The upper band changes the shoulder outline in a way that is different from ordinary straps. Its material, attachment method and ability to move are not established by this standing view.
If this is the detail you want, ask to try the band during ordinary gestures. Reach toward a table, raise your hands for a greeting and let the arms settle. Notice whether you want to rearrange the band afterwards. Ask whether any proposed adjustment changes the neckline as well as the arm section, rather than assuming the band can be moved independently.
Keep the band in your material questions too. The composition of the skirt would not automatically describe this upper element or its lining. Request information for the exact model. A useful fitting note records how the arm detail behaves and what is known about its construction, without calling it bamboo or environmentally preferable from appearance.