It is the Chinese method of balancing the yin and the yang to help attract more of the positive energies in life. It usually applies in arranging a house or a building by proper positioning of certain items i.e. furniture and creating a breathable and balance space.
In Chinese, "Feng" means "wind" and "Shui" means "water". These two are related to maintaining good health and so good health means good fortune. And, balancing space with wind and water, means a balance life.
I hope it helps.