how to wait for seconds in unity c$ code example

Example 1: Time delay C# unity

void start()
StartCoroutine(Text());

IEnumerator Text()  //  <-  its a standalone method
{
	Debug.Log("Hello")
    yield return new WaitForSeconds(3)
    Debug.Log("ByeBye")
}

Example 2: wait for seconds unity

//In the example below the script will right "Hello" and 3 seconds later write "Goodbye" in the console
Start()
{
  	//Call the function Example()
	StartCoroutine(Example());
}

Example()
{
  	Debug.Log("Hello");
  	//wait 3 seconds
	yield return new WaitForSeconds(3);
  	Debug.Log("Goodbye");
}