It refers to the additional fabric or material that is left during the tailoring or sewing process. It is the allowance provided beyond the actual measurements or dimensions of the garment. The purpose of leaving a margin is to allow for adjustments or modifications if needed. The margin provides flexibility to make changes to the size or fit of the garment by adding or removing fabric as necessary. It ensures that the garment can be tailored or altered according to specific measurements or preferences without compromising the overall design and structure.