Nobody knows exactly why we dream when we sleep. All we know is that everyone dreams, although most dreams aren’t avoid enough for us to remember them when we wake up. Dreams are not messages from other world, or prophecies of what may happen in the future, but very often the result of what we have been thinking about when we were awake, sometimes without us realizing that we are thinking about it. For example, if we go to bed tired, cold or hungry, these feelings may well appear in our dreams.
There is a tale about a man who went to bed hungry. He dreamed that he was eating a breakfast cereal, and when he woke up, he fauna that he had eaten some of his mattress! This is almost certainly not a true story, but it shows you an example of this link between our emotions and our dreams. We may also have dreams about the things we like best, or nightmares about the things we hate or fear. This is why many young children dream about fairies or witches, and why homesick people dream about their families or homes.