The journey of a GraphQL query begins with the client sending a request to the server, which is defined by a schema that outlines the available data and its structure. The schema serves as a contract between the server and the client, ensuring that only valid data is returned. Upon receiving the query, the server validates it against the schema, extracting the requested fields from an Abstract Syntax Tree (AST) representation of the query. If the query is deemed invalid, the server returns an error to the client; otherwise, it invokes resolver functions associated with each field in the query, which retrieve data from data sources such as databases or REST APIs. The retrieved data is then assembled into a JSON object that matches the shape of the original query, and this data is returned to the client, which renders it using components built on top of the received data.