fix: setImmediate docs

Author: pakobarbakadze

apps/site/pages/en/learn/asynchronous-work/discover-promises-in-nodejs.md

@@ -367,21 +367,31 @@ console.log('Synchronous task executed');
 
 ### `setImmediate()`
 
-`setImmediate()` is used to execute a callback after the current event loop cycle finishes and all I/O events have been processed. This means that `setImmediate()` callbacks run after any I/O callbacks, but before timers.
+`setImmediate()` schedules its callback for the event loop’s check phase—i.e. it will run immediately after all of the current loop’s I/O callbacks (poll phase) have completed.
 
 ```js
+const fs = require('fs');
+
 setImmediate(() => {
   console.log('Immediate callback');
 });
 
+fs.readFile('./some.txt', () => {
+  console.log('I/O callback (file read)');
+});
+
+setTimeout(() => {
+  console.log('Timeout callback')
+}, 0)
+
 console.log('Synchronous task executed');
 ```
 
 ### When to Use Each
 
 - Use `queueMicrotask()` for tasks that need to run immediately after the current script and before any I/O or timer callbacks, typically for Promise resolutions.
 - Use `process.nextTick()` for tasks that should execute before any I/O events, often useful for deferring operations or handling errors synchronously.
-- Use `setImmediate()` for tasks that should run after I/O events but before timers.
+– Use `setImmediate()` for tasks that should run after the current event loop’s I/O events, but before timers scheduled for the next loop iteration.
 
 Because these tasks execute outside of the current synchronous flow, uncaught exceptions inside these callbacks won't be caught by surrounding `try/catch` blocks and may crash the application if not properly managed (e.g., by attaching `.catch()` to Promises or using global error handlers like `process.on('uncaughtException')`).