Guy Korland's blog post explains the process of building and querying a knowledge graph from unstructured data using Diffbot API, FalkorDB, and LangChain. Diffbot API transforms unstructured documents into structured data, creating a knowledge graph that maps entities and their relationships, which is then stored in FalkorDB. LangChain is utilized to query this graph, offering the capability to handle complex, natural language queries and provide accurate answers. The post includes instructions on setting up the necessary tools, such as installing LangChain and running a local FalkorDB server, as well as a demonstration of creating a knowledge graph about Warren Buffett using Wikipedia data, storing it in FalkorDB, and querying it with LangChain. Guy Korland, CEO of FalkorDB, leverages his extensive background in database engineering and AI to guide readers through these steps, emphasizing the integration of these technologies to enhance data retrieval and decision-making processes.