The internet and a Network

What is the Internet?
The internet is a global network that provides a variety of information and communication sources. It enables computers to send one another small packets of digital data.

WWW and the internet 

The internet is a global network that provides a variety of information and communication systems, one of these information systems(web pages)are called the World Wide Web.

The difference between them is that the World Wide Web is provided by the internet. 

What is a Network?

A network (computer network) is a group of two or more computer systems (mobile phones, printers etc.)  which are all linked together. The two main types of networks are called LAN (local area networks) and WAN (wide area networks).

Using radio waves, copper wires and many other things, you are sharing data (pictures, emails, files, documents, videos etc.) between different computer systems.