A connection between two end points, either physical or logical, over which data may travel in both directions simultaneously is called
A connection between two end points, either physical or logical, over which data may travel in both directions simultaneously is called Duplex.
When one device is sending, the other can only receive, and vice versa. In full-duplex mode (also called duplex), both stations can transmit and receive simultaneously the full-duplex mode is like a two way street with traffic flowing in both directions at the same time.
The primary difference between three modes of transmission is that in a simplex mode of transmission the communication is unidirectional or one-way whereas, in the half duplex mode of transmission the communication is two-directional, but the channel is interchangeably used by the both the connected devices.
Full-duplex data transmission means that data can be transmitted in both directions on a signal carrier at the same time. For example, on a local area network with a technology that has full-duplex transmission, one workstation can be sending data on the line while another workstation is receiving data.