GraphQL is a query language that provides a flexible and robust way to ask for data, allowing developers to use JavaScript to execute queries anywhere. GraphQL.js is the reference implementation of GraphQL in JavaScript, adhering to the official GraphQL specification. To get started with GraphQL.js, install the library using npm or Yarn, create a new project folder, initialize a Node.js project, and write code in an index.js file. The example demonstrates how to construct a schema, define resolvers for fields, and run queries using JavaScript. Once installed, running the query results in a response with the requested data, providing a foundation for building GraphQL APIs with JavaScript.