Callbacks are entities that must be handled when executing an application. In the case of Node.js, this is accomplished using event loops. This is a critical feature to have because Node.js allows non-blocking transmit.
An event loop starts operating when a callback occurs somewhere in the middle of an event. A specific listener is generally in charge of this. After the functions have been called, Node.js will continue to execute the code without waiting for the output.
After all of the code has been run, the outputs have been obtained, and the callback function has been run. The name event loop comes from the fact that it functions in the form of a continuous loop.