srs.txt

For example, a function to read a file may start reading file and return the control to the execution environment immediately so that the next instruction
can be executed. Once file I/O is complete, it will call the callback function while passing the callback function, the content of the file as a parameter.
So there is no blocking or wait for File I/O. This makes Node.js highly scalable, as it can process a high number of requests without waiting for any
function to return results.