A two-way radio is simply a radio that can both transmit and receive (a transceiver). Portable two-way radios are often called walkie-talkies or handi-talkies. Two-way radios are also available in mobile and base configurations. An example of a two-way radio that both transmits and receives at the same time (or full-duplex) is a mobile phone or cellular telephone, which uses two different radio frequencies to carry the two directions of the conversation simultaneously.
Two-way radios can operate on many different frequencies, the most common ones being FRS (Family Radio Service) and GMRS (General Mobile Radio Service). The channels that FRS operate on range from 1 to 14, and if a specific radio is equipped, there may also be GMRS channels, ranging from 15 to 22.