This the communication between computer systems or devices. A computer network is any set of computers or devices connected to each other with the ability to exchange data.
Data Communication is the process of transferring information from a sender to a receiver with the use of a medium in which the communicated information is understood by both sender and receiver. It is a process that ALLOWS organisms to exchange information by several methods. 
Telecommunications is a general term for a VAST array of TECHNOLOGIES that send information over distances. Mobile PHONES, land lines, satellite phones and voice over Internet protocol (VoIP) are all TELEPHONY technologies -- just one field of telecommunications. Radio, television and networks are a few more examples of telecommunication.

This the communication between computer systems or devices. A computer network is any set of computers or devices connected to each other with the ability to exchange data.
Data Communication is the process of transferring information from a sender to a receiver with the use of a medium in which the communicated information is understood by both sender and receiver. It is a process that allows organisms to exchange information by several methods. 
Telecommunications is a general term for a vast array of technologies that send information over distances. Mobile phones, land lines, satellite phones and voice over Internet protocol (VoIP) are all telephony technologies -- just one field of telecommunications. Radio, television and networks are a few more examples of telecommunication.