Simple Definition:

A computer network is a collection of computers and other digital devices that are connected together to share resources and information. Computer networks allow devices to communicate and exchange data with one another. Examples of computer networks include local area networks (LANs), wide area networks (WANs), and the internet.

Very Simple Definition:

This is a group of computers that are connected together so they can communicate and share information with each other. An example is a network of computers in an office that allows employees to share files and printers.