In computing, linked data describes a method of publishing structured data so that it can be interlinked and become more useful. It builds upon standard Web technologies such as HTTP and URIs, but rather than using them to serve web pages for human readers, it extends them to share information in a way that can be read automatically by computers. This enables data from different sources to be connected and queried.

Here is a brilliant non-technical introduction to Linked Data, Google’s Knowledge Graph, and Facebook’s Open Graph Protocol by @manusporny that you should watch.