It is the Semantic Web done right.
Wikipedia defines Linked Data as “a term used to describe a recommended best practice for exposing, sharing, and connecting pieces of data, information, and knowledge on the Semantic Web using URIs and RDF.”
It is 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.
Linked data, in the form of structured, typed, and dereferencable links, powers media sites for organizations such as the BBC and New York Times; major libraries and museums around the world actively develop their content as linked data.
Google, Yahoo!, Microsoft, Facebook, many other large Web companies as well as numerous research projects are developing large knowledge graphs, which define, structure, and link hundreds of millions of entities, to enhance search, to provide better advertising match, to improve the answers of their artificial personal assistants, and so on.