GraphQL is a versatile standard for defining, querying, and documenting APIs in an intuitive manner, offering a user-friendly query language and integrated documentation. The guide outlines how Buildkite utilizes GraphQL for front-end development, demonstrating how users can create scheduled builds, a feature not yet available via the web UI, using GraphQL queries and mutations. It introduces GraphiQL, an open-source GraphQL explorer that facilitates testing and exploring APIs with features like auto-complete and inline documentation. Users can execute queries to retrieve user information or build details, and leverage variables for more dynamic and reusable queries. The text also explains the implementation of GraphQL mutations to automate tasks like creating build schedules with required fields such as pipelineID, label, and cronline specified in Cron syntax. Examples include running queries and mutations via cURL, emphasizing GraphQL's simplicity in using HTTP requests to send and retrieve JSON data. The document concludes with additional resources for learning more about GraphQL.