Coroutines and Yield - Unity 4 Game Development - page 613

WaitForSeconds
WaitForSeconds suspends the coroutine execution for the given amount of
seconds.
WaitForSeconds can only be used with a yield statement in coroutines . An ex-
ample of WaitForSeconds is as follows:
// JavaScript user:
function Start() {
// Prints 0
Debug.Log (Time.time);
// Waits 5 seconds
yield WaitForSeconds (5);
// Prints 5.0
Debug.Log (Time.time);
}
// C# user:
IEnumerator Start() {
// Prints 0
Debug.Log (Time.time);
// Waits 5 seconds
yield return new WaitForSeconds (5f);
// Prints 5.0
Debug.Log (Time.time);
}
You can both stack and chain coroutines .
The following example will execute Do() . We will see that it will call the first line in
Do() . Then, it will call the last line in Start() immediately, while waiting for 5 seconds
to call the last script in Do() .