In a higher level lucid dreaming, the dreamer fully understands they are dreaming and can actually take control of their dreams, understanding that their dream poses no risk. Often times people who experience high level lucid dreams utilize these dreams to fulfill fantasies such as flying or activities that would pose risk in real life.
Once people learn that they can control their dreams, many people try to learn how to become a lucid dreamer. Unfortunately, the older you get, the harder it is to learn how to lucid dream. So if you are younger, there is no better time than the present to immerse yourself in learning the techniques required to lucid dream. Imagine if you always had control of your dreams, it would be like being awake 24 hours a day!
To learn more about lucid dreaming, check out Stephen Laberge's book 'Exploring the World of Lucid Dreaming' or rent the movie 'Waking Life'.