The original database for the Google Knowledge Graph was Freebase, which Google acquired through the acquisition of Metaweb in 2010. This in turn was replaced by Wikidata in December 2014. The Freebase data flows into Wikidata, which is one of the most important databases for the Google Knowledge Graph. The Google Knowledge Graph contains information about people, places, organizations, events and things. It is an example of how machine learning algorithms can draw conclusions based on large amounts of structured and unstructured data. In addition to Wikidata, the Google Knowledge Graph is fed by a variety of different data sources, including Wikipedia and the CIA World Facts Book. Any website that has a certain structured format, in addition to authority and credibility, is suitable as a potential data source. Examples include Google My Business and event platforms. The Knowledge Graph is additionally enriched with information from Google's own data sources, such as Google Maps and Google Places. Structured data tagged with JSON-LD can also be used as an additional source.