Answer:
Relief sculpture is a complex art form that combines many features of the two-dimensional pictorial arts and the three-dimensional sculptural arts. On the one hand, a relief, like a picture, is dependent on a supporting surface, and its composition must be extended in a plane in order to be visible.
sculptural relief in which the outlines of modeled forms are incised in a plane surface beyond which the forms do not project. 2 : sculpture or a sculptural form executed in sunk relief.