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.
All users of the Internet will be familiar with the concept of hypertext links, the way that a link on one web page is able to guide the browser to loading another page from a known location.
Whilst humans are able to understand relationship discoverability and how links work, computers find this much more difficult, and require a well-defined protocol to be able to traverse from one data element to another held in a separate location.
Creating a system of readable links for computers requires the use of a well defined data format (JSON-LD) and assignation of unique IDs (URLs or URNs) for both data entities and the relationships between entities so that semantic meaning can be programmatically retrieved from the data itself.
Properly defined linked data can be used to help answer big data questions, and the data relationships can be traversed to answer questions like "Which products are currently available on the shelves of Store X and what prices are they sold at?"