The JavaScript runtime environment is a single-threaded, non-blocking event loop that provides concurrency by using events and callbacks to handle asynchronous requests. This allows JavaScript programs to execute asynchronously without blocking the execution of other code on the stack. The callback queue plays a crucial role in this process, allowing external APIs to communicate with the JavaScript engine and providing a mechanism for asynchronous functionality. By understanding how the event loop and callback queue work together, developers can build JavaScript applications that make use of external APIs without freezing their application while waiting for an API response. The post demonstrates how to use callbacks to perform complex series of data queries from remote sources, showcasing the power of asynchronous programming in JavaScript.