The Event loop in Node.js handles all asynchronous callbacks in an application.
It is an essential part of Node.js as Node.js (or JavaScript) is a single-threaded, event-driven language.
A listener can be attached easily to an event with the callback provided by the listener when the event occurs.
All callbacks functions are queued on a loop and then executed after the other after the response has been received.
When functions like setTimeout, fs.readFile, and HTTP.get are called, the event loop is executed by Node.js, and it continues with further code without waiting for output.
Once the operation is finished, it receives the output and then runs the callback function.