Symmetric & Asymmetric and sending Module?

Explain Symmetric & Asymmetric communication, what is mean by 'sending module logically dealing with specific recieving module'?

The term symmetric refers to any system in which data speed or quantity is the same in both directions.

For Example: two-way radio, standard twisted-pair telephone Internet connections, cable modem.

The term asymmetric refers to any system in which the data speed or quantity differs in one direction as compared with the other direction, averaged over time.

Consider an Internet connection in which downstream data from an Internet server to the subscriber flows over a broadband satellite downlink, while upstream data from the end user to the server is sent over a twisted-pair telephone line. This is an example of asymmetric communications.

It means sender and receiver have coordination with each other for sending/receiving data.