Fractionation means getting a person into trance state, emerge him and again put him in trance state. It may be done a few rounds. The objective is to put the hypnotized person into a deeper trance.
Have you been awaken by alarm clock before? You sleepily open your eyes, look at the time, turn off the alarm and return back to sleep. You felt so sleepy that you don’t wish to wake up. This is fractionation.
The difference is one is deliberately induced by a hypnotist while the other occurs naturally.