层叠 is a verb phrase meaning 'to pile up in layers' or 'to be stacked one on top of another'. You can use it to describe physical objects like papers, clouds, or mountain ranges where multiple layers are visible. It often appears with 起来 to indicate the action of stacking, or as a modifier before a noun (层叠的山峰 'layered peaks'). The English phrase 'one on top of another' captures the idea but is not a natural equivalent—层叠 is a single concise verb concept in Chinese.