An emergency radio is, broadly speaking, a radio receiver designed to remain functional in cases of a power outage or isolation from contact with civilization. Such radios are often designed to run on minimal or renewable power sources, such as solar.
Rely on emergency and weather radios as well as locator beacons to help rescue teams locate you in an emergency situation.
Emergency radios are generally designed to cover the standard AM and FM broadcasting bands, and weather radio in countries that provide that service. Basic shortwave radio coverage (for situations where local radio is out or not available) is less common.