面额 has two major uses. The more common one is in finance, where it refers to the stated value printed on a banknote or coin (the denomination). The other, less frequent use is a formal or literary term for the forehead (the area of the face above the eyes). In modern Chinese, 'forehead' is usually 额头, so you'll encounter 面额 mostly in financial contexts — bank statements, currency design, or when talking about money amounts.