On a telephone, the handset is a device the user holds to the ear to hear the audio sound. Modern-day handsets usually contain the phone's microphone as well, but in early telephones the microphone was mounted directly on the telephone itself, which often was attached to a wall at a convenient height for talking. Handsets on such telephones were called receivers, a term that is often applied to modern-day handsets, also.
Until the advent of the cordless telephone, the handset was usually wired to the base unit, typically by a flexible tinsel wire.
A cordless telephone uses a radio transceiver as its handset, and a radio transceiver, wired to the telephone line, as a base station. In a mobile telephone, the entire unit is usually a radio transceiver that communicates through an outdoor base station located at a cell site. Some mobile telephones that can be carried in cars, trucks, and buses look exactly like household telephones, except that their bases are usually screwed or bolted to the interior of the vehicle.