fix(learn): improve the learn Asynchronous Work doc

apps/site/pages/en/learn/asynchronous-work/understanding-processnexttick.md

@@ -25,31 +25,33 @@ Calling `setTimeout(() => {}, 0)` will execute the function at the end of next t
 
 Use `nextTick()` when you want to make sure that in the next event loop iteration that code is already executed.
 
-#### An Example of the order of events:
+#### An Example of the [order of events](https://nodejs.org/en/learn/asynchronous-work/event-loop-timers-and-nexttick):
 
 ```js
 console.log('Hello => number 1');
 
 setImmediate(() => {
-  console.log('Running before the timeout => number 3');
+  console.log('Running at order 3 or 4, setImmediate');
 });
 
 setTimeout(() => {
-  console.log('The timeout running last => number 4');
+  console.log('Running at order 3 or 4, setTimeout');
 }, 0);
 
 process.nextTick(() => {
   console.log('Running at next tick => number 2');
 });
 ```
 
-#### Example output:
+#### Example output(possible):
 
 ```bash
 Hello => number 1
 Running at next tick => number 2
-Running before the timeout => number 3
-The timeout running last => number 4
+Running at order 3 or 4, setImmediate
+Running at order 3 or 4, setTimeout
 ```
 
-The exact output may differ from run to run.
+In that case, `console.log('Hello => number 1');` will first run because event loop only starts after call stack is cleared.The `nextTick` queue is processed before entering the next phase, which is why the `process.nextTick()` callback runs immediately after.
+
+The execution order of `setImmediate()` and `setTimeout()` can very based on the execution contexts. For more information, refer to [`setImmediate()` vs `setTimeout()`](https://nodejs.org/en/learn/asynchronous-work/event-loop-timers-and-nexttick#setimmediate-vs-settimeout).