In data communication and networking, data transmission can be in one of three modes between two parties
simplex
half-duplex and
full-duplex
In Simplex mode transmission is only in one direction. One of the parties is strictly a sender or a receiver and cannot be both. Typical examples are keyboards and monitors
In half duplex both parties can send and receive data, however it has to be one at a time as communication is one way at a time, so it is when one party completes its transmission that the second party begins. A good example is the Walkie-Talkie device
In the full-duplex mode sending and receiving happens simulteneously with the cellular phone being a good example.
