Why do we dream?

People always have dream while they are sleeping. But where do dream go when we wake up? We have dream every nigh, whenever we remember it or not. Sometime the event that have been happen or you always think about it, the brain can not forget it, so when we sleep in the night, those event come to your dream, it is your amazing. Moreover, when we are wide awake our sense of time is vertical. So that we are aware only of the present moment, but that when we are asleep, time becomes for us horizontal, so that we can travel into the past and the future. Consequently, we try to realize inour sleep wishes that cannot be realized by day.