Linked Data empowers people that publish and use information on the Web. It is a way to create a network of standards-based, machine-readable data across Web sites. It allows an application to start at one piece of Linked Data, and follow embedded links to other pieces of Linked Data that are hosted on different sites across the Web.
JSON-LD is a lightweight Linked Data format. It is easy for humans to read and write. It is based on the already successful JSON format and provides a way to help JSON data interoperate at Web-scale. JSON-LD is an ideal data format for programming environments, REST Web services, and unstructured databases such as CouchDB and MongoDB.
The Knowledge Graph is Google’s system for organizing information about millions of well-known “entities”: people, places, and organizations in the real world. Google’s algorithms merge information about entities from many data sources. For some types of information, though, the best source of data is the entity itself.
Specifically, companies and people can now customize their own data in the Knowledge Graph by adding structured data markup to their official website. The following types of data may be customized:
link tools for google graph =>
introduction tutorial 1. http://www.seoskeptic.com/json-ld-big-day-at-google/