A transceiver is a device that has both a transmitter and a receiver which are combined and share common circuitry or a single housing. Similar devices include transponders, transverters, and repeaters.
In radio terminology, a transceiver means a unit which contains both a receiver and a transmitter.
It was quite common to have these units separated. Ham radio operators can build their own equipment and it is always easier to design and build a simple unit having one of the functions, transmitting or receiving. Almost every modern amateur radio equipment is now a transceiver but there is an active market for pure radio receivers, mainly for shortwave listening operators.
The term originated in the early 1920s. Technically, transceivers must combine a significant amount of the transmitter and receiver handling circuitry. An example of a transceiver would be a walkie-talkie, or a CB radio.
A walkie-talkie (more formally known as a handheld transceiver) is a hand-held, portable, two-way radio transceiver. If no circuitry is common between transmit and receive functions, the device is a transmitter-receiver. Its development during the Second World War has been variously credited to Donald L. Hings, radio engineer Alfred J. Gross, and engineering teams at Motorola.
Similar designs were created for other armed forces, and after the war, walkie-talkies spread to public safety and eventually commercial and jobsite work. Major characteristics include a half-duplex channel (only one radio transmits at a time, though any number can listen) and a "push-to-talk" (PTT) switch that starts transmission.