It is used mainly for chaining lucid dreams. Basically, you become lucid within a dream and once the dream comes to a close, you can dream chain (perform a DEILD and enter back into a lucid dream). Another time to perform this technique, is if you have woken up (or are waking up) and you haven't opened your eyes or anything yet. Alot of times you will become aware/conscious as you are waking from a normal dream. If this happens you should attempt a DEILD and enter directly into a lucid.