EUA is a tool used by FDA to authorize the temporary use of products that fulfill urgent medical needs during public health emergencies. These products are authorized for use only in specific circumstances and expire once those conditions end.
EUA plays an important role in an emergency response because it can enable public health officials and physicians to use the best countermeasure available to detect, prevent, or treat a disease or injury in certain populations, even if that countermeasure is unapproved by the FDA or not approved for that particular use.
It is also important to keep in mind that EUA is about getting authorization, not about getting clearance or approval. In general, an EUA will remain in effect only for the duration of the EUA declaration under which it was issued. Sponsors should continue to develop their product, working towards FDA approval after the termination of the emergency.
References : Camargo, Greenlight Guru, NCBI