The World Wide Web that we browse consists of human readable web pages. However, the web was originally conceived in CERN as a way to share data. Berners-Lee, Tim's vision is for a web of data that is machine readable, so that automated systems and reasoning can apply at a global scale. Central to this vision is the semantic web, which means that not only the data itself, but also the meta-information necessary to interpret it, are available in a machine readable and linkable fashion.
Used in Chap. 17: page 250