Data Communication System Definition?

I could not understand the difintion of "Data Communication System" 

Communication means a “to share”. Data communication is actually sharing of information, knowledge and important data.

For example: we want to send a file to our Boss. We prepare it and deliver it to Boss by hand or by post or by a peon, this is called data communication. In similar way we can send it through computer (via email) considering that we are working on modern technology.

So data communication is a sharing, distribution of information where some person will send (sender entity), someone will receive (receiver entity) and there will be the medium (wire, air, peon) who transfer this information.