Sir Tim Berners Lee invention World Wide Web (WWW) is a gigantic space of information spanning over the whole world in which every item (or resource) is identified by a "Uniform Resource Identifier." (URI) The best example to illustrate this is that a real World wide web address always begin with http://, which is one of these "resource identifier". Other URIs are the ftp protocols (for file transfer), the mailto protocol (for emails), etc. Every single web page, image or any other form of data possesses a unique "address" on the world wide web. Some people consider that the World Wide Web and the Internet are both the same thing. It is however not the case. As a matter of fact, the World Wide Web is only a sub-part of the whole Internet network. When you play games for example, you're still connected to the Internet but you do not necessarily transfer data using the World Wide Web. To conclude, keep in mind that the World Wide Web is an information space to which every item is linked by a Uniform Resource Identifier (URI). The World Wide Web and the Internet are both different things, as the World Wide Web is a sub-part of the Internet.
It is a system of extensively interconnected data on the internet