Say it like this

A group of things connected together so they can pass messages to each other.

For the grown-up

A network is a set of connected nodes and the links between them. The idea is not specific to computers. Roads are a network, so are friendships, and the same rules about connections and reach apply to all of them.

The easy mistake

Careful here. The value of a network usually comes from the connections rather than the things being connected. One phone is useless. Two is a conversation.

Words next to this one

Internet Computers talking to other computers. All of them, all over the world, all the time. Server A computer whose whole job is holding things and handing them over when somebody asks. Computer A machine that follows instructions very fast and never gets bored of doing the same thing again. Website A place on the internet where somebody keeps their things so other people can come and look.