受命 is a formal verb-object compound meaning 'to receive orders' or 'to be entrusted with a mission'. It is a separable verb (离合词): when you need to insert a modifier, duration, or other element, the components separate — e.g., 受了一次命 ('received orders once'). It typically appears in official or historical contexts, such as reporting to a superior or accepting a formal duty. The object is often implied or explicit (like 命令), but 受命 alone carries the full meaning.