5 element Theory 
Everything in the universe is made up of 5 elements and how they relate to each other causes energy near them to become either auspicious or inauspicious. Element harmony or disharmony creates either "Good" or "Bad" feng shui.
The 5 Elements:

The Productive Cycle
When the elements are combined in the environment to work together in HARMONY, the result are success, prosperity, abundance, happiness, satisfaction, health and harmonious relationships. This is when "everything in life is working very smoothly".

    The Productive Cycle:
    Water Produces Wood
    Wood Produces Fire
    Fire Produces Earth
    Earth Produces Metal
    Metal Produces Water

The Destructive Cycle
When the elements CLASH when combined together in the environment, the result can cause accidents, illness, job loss, missed opportunities, failed relationships and financial problems. This is when "everything seems to go wrong" at the same time.

    The Destructive Cycle
    Water Destroys Fire
    Fire Destroys Metal
    Metal Destroys Wood
    Wood Destroys Earth
    Earth Destroys Water

The Exhaustive Cycle
There is also a subtler, yet potent "Exhaustive Cycle" to be aware of that may drain energy from your goals. This cycle is sometimes utilized by experienced Feng Shui practitioners to purposely reduce the negative energies in a certain location. You will notice that the Exhaustive Cycle is the opposite of the Productive Cycle.

    The Exhaustive Cycle
    Wood Exhausts Water
    Water Exhausts Metal
    Metal Exhausts Earth
    Earth Exhausts Fire
    Fire Exhausts Wood

The Cosmic Trinity
Ancient Chinese believe that three forces influence our lives: Heaven Luck, Man Luck and Earth luck. 
Heaven Luck is that with which we are born; when someone refers to your Destiny, they mean your Heaven Luck. There are various ways in which to chart out a person's Heaven Luck. One of the more popular methods in Chinese Astrology is known as BaZi or Four Pillars of Destiny.
Heaven Luck is believed to be an unchangeable aspect of our lives and this affects 33% of our lives.
Man Luck is the effort that we put into shaping our lives. It is an aspect of our lives over which we have full control. By taking initiatives, by persevering in the face of difficulties; by our virtues and deeds, we can determine the course our lives will take. The power of positive thinking taking the right actions and striving for what we want are all the various facets of Man Luck. The choices that we make in our lives affect 33% of it's outcome.
Earth Luck is the essence of Feng Shui. It is a reference to how we can employ the energy and forces of Nature within our environment to support us in our goals and everyday activities. Environmental factors that affect our lives include the external environment outside our living and working space as well as the internal environment within our homes and offices. By applying Feng Shui principles and applications, we can bolster the positive aspects that Heaven Luck presents us and diminish the negative cycles in our lives.

Feng Shui is knowledge, the practice of Feng Shui is a SKILL. Feng shui symbols and images
Feng shui symbols and images can help you harmonizing and balancing the elements within your home and improve your life quality. Feng shui symbols are an important feng shui tool which you have to take into account at the time to look for balance and harmony in your house in a good looking way.
By placing the proper feng shui symbols, you can add a necessary element, color, or anything which is symbolized in any place. By doing this and following the bagua map indications, you can equilibrate and improve the different areas of your life by just placing the symbol or image throughout the place.
Feng shui symbols come in many different ways. But what matters the most is the symbol or image itself and what it represents. You should always know what the symbol you choose means and what should it be used for. This way, feng shui symbols provide a good way of adding elements and objects in order to create the wished harmony within any living or working space.

What is Feng Shui
Feng Shui is the ancient Chinese philosophy and practice of understanding the movement of energy in our environment.  Feng Shui is about achieving life-fulfillment by benefiting from the energies of our living environment and living in harmony with nature. By living in harmony, we are able to benefit from energy (known as Chi or Qi) to better our lives.
Feng Shui means wind and water, which are the two fundamental forms of life energy. Feng Shui studies life energy, the movement of energy in our environment and how the design of buildings and interiors affects us in a subtle manner. Feng Shui uses positive 'chi' to improve an individual's good luck and success.

Chi is an ancient Chinese concept which teaches that there is energy constantly flowing everywhere. 'Chi' is the energy that connects people with their environment. 'Chi' is present everywhere, around the earth, in the atmosphere and is present in and around our body. This energy is constantly in a state of flux as a result we are constantly changing though we are unaware of it. This change is essential for out mental, physical and spiritual health. When there is no change there is stagnation. Whenever chi finds obstacles for circulating we will notice it since it will directly affect our lives. Our life quality can diminish or be improved depending on the way chi flows in the environments we inhabit.
According to feng shui, chi should always be able to flow freely through any space in order to help us being in balance with the elements surrounding us. Chi is what brings us positive energy and allows us to be prosperous in our lives. Chi is based on the natural energy exchange which exists among everything on earth, and it shouldn't be blocked.
This way, a person who feels upset or depressed should pay attention to the chi flow within his house. When we are feeling ill or like our life is not flowing as it should, this might be due to chi circulation problems. By spotting the obstacles that may not allow chi circulate freely and then ending up with them, we will be bringing the right fluidity to chi and to our lives along with it.
Feng shui studies how to help chi flow in the best possible way within living or working environment in order to maximize the life quality of those who inhabit those spaces. Depending on the way objects are placed and distributed within environments, they would help or block the natural chi circulation. Therefore, we need to make sure they are placed in the correct way and that is what feng shui does.
When chi is blocked by finding too many objects on its way, it might not only be unable to flow freely but it might also even become stuck at some spots. When chi is detained, the life flow of those who inhabit that space would become detained as well, making them feel they are not moving on or succeeding in achieving new goals. Feng shui helps people overcoming and preventing all these chi flow problems.
'Chi' can take the form of matter or energy or can be a combination of the two. Thus 'chi' can be visible, partially visible, invisible or partially invisible. 'Chi' is present in everything we do, see and in everything that surrounds us. Each of us has 'chi' within us. This 'chi' gives our body energy.  'Chi' energy is vital for maintaining physical, environmental and emotional balance. When 'chi' in your body is blocked or there is an imbalance of energy, then you may feel ill, depressed or have physical discomfort. When the 'chi' in your environment is out of balance, it will affect your life. This may cause disturbance in your relationships or difficulties in business or cause general ill luck. In Feng Shui we can find connection between the quality of a person's life and the environment in which he lives and works. 
When 'chi' is balanced and flowing properly then it is called Sheng Chi. It brings luck, happiness, new opportunities and all the good things in life. Unlucky 'chi' is called Sha Chi. This is unbalanced energy and will cause problems, illness and setbacks etc. Sha Chi may be obvious or something you cannot pin point. Living under the influence of Sha Chi can be detrimental to your welfare. The concept of Yin and Yang
The concept of Yin and Yang is integral to Feng Shui. Yin and Yang are considered to be two complementary forces described as the two basic and interactive forces of nature. Yin and Yang represent the two poles of existence that create the dynamic impetus of all life. They are the two poles of universal energy that interact to give rise to all of creation.
To maintain balance there should be harmony between these two forces. All things are a constantly shifting combination of yin and yang, which is always seeking balance. Because balance can never be reached permanently, yin and yang continuously shift and life continues to flow unceasingly. The concept of yin and yang explains the change in all things. One force cannot exist without the other. We cannot understand one without the other for example we cannot understand light without darkness, joy without sorrow etc. Each force acts on the other force to initiate movement. Nothing in this world is totally yin or totally yang. According to Feng Shui we need to balance the yin and yang in each room of our home. If a room is painted with dark colors, is cold and has very little sunlight in it is considered to be too yin or have stagnant 'chi'.  In contrast if a room is painted with light colors, very bright and very warm, it is considered to have too much yang 'chi'.