Vastu is connection between living and non living things. That means there is some energy between human and the things that everyone is attached in day to day life.
Whether knowingly or unknowingly in routine life we are connected to so many objects which are important in our life. Coming to the main point every object has some vibrations for us and on the other hand we have vibrations also for those things.
This effect of vibration between you and non living things could be positive or negative depending upon their structure, colour, actions, uses and planetary connection. The art of making beautiful vibrational connection between you (living creature) with nature and nonliving things is called Vastu.