The belief in Feng Shui is that there is energy that travels around the world called Chi this is also called Ki or prana.
When the chi is travelling at a certain speed all around is fine. When it is too slow, or it has stopped it stagnates everything. If the chi is running too fast it is aggressive.
Imagine chi as water, travelling at the correct speed it is a bubbling brook full of life yet calm enough for plants to grow. Too fast and it is the rough sea crashing into the rocks unpredictable and dangerous. No movement and it is a pond that is overgrown with algae, everything is lifeless. The pond, and all the pond life is choking.
The chi meandering around the house is fine, blockages in the form of clutter or too many objects slow down the chi until it reaches stagnation point.
When the chi is travelling too fast then you will find that the occupants never seem to settle they are always on the go, or totally worn out.
A typical bad point of most houses is that the stairs lead directly onto the front door. This causes all the chi that is travelling around to come to the stairs and rush straight through the front door when it is open. Most of the energy is emptied every time the front door is opened. This problem is easily remedied - a metal hollow wind chime will deflect the energy back around the house.
Chi running down straight narrow corridors runs too fast, by putting mirrors staggered either side of the corridor the chi sweep left to right, and thus slows down.
Balancing and enhancing chi is the main part of Feng Shui once this is achieved the house becomes more like a home.