Callback Queue VS Microtask Queue 

In this lecture, you will understand the use and difference between callback queue and microtask queue. In the last lecture, you learned:
1. A callback function associated with an asynchronous task has to wait for there execution.
2. It waits inside either a callback queue or microtask queue for its execution.
3. The event loop pushes callback functions to call stack for their execution when call stack is empty.
Let's understand these steps in a more detailed manner.