"The Secret" is both a book and a movie, written and produced by Rhonda Byrnes.  Due to its rapid underground popularity and because of its significant message, it was featured on the Oprah show twice in February 2007 with 5 guests from "The Secret" and 2 returning guests.  The first guests on Oprah's show were Rhonda Byrnes, Jack Canfield, Lisa Nichols, James Arthur Ray, and Reverand Dr. Michael Beckwith, with James Arthur Ray and Rev. Dr. Michael Beckwith returning for the follow up show.

The movie features some 20 or so experts on "The Secret" from authors, entrepreneurs, etc. to doctors, quantum physicists, etc., all who successfully use The Secret in their lives.  It also features famous historic quotes from Albert Einstein, Henry Ford, and more (see http://goodkarma.org/node/150) that seem to support The Secret.

The Secret, as described by Rhonda Byrnes on the Oprah show, is "the Law of Attraction, or the universal principle that like attracts like."  The Law of Attraction can be described in many different ways - "what you focus on expands," "what you think about and thank about you bring about," "thoughts become things," our thoughts create our reality, "energy flows where attention goes," "man becomes what he thinks about," etc.  And more so than our thoughts, it is our feelings that really create our reality - it's more what your feeling about than thinking about.  (This is why it's not exactly about "positive thinking" since it's easy to say things to ourselves even when we don't feel them - it's only what feels real to you that becomes reality.)

The way to use The Secret (the Law of Attraction) is 1. Ask, 2. Believe, 3. Receive, or "Intention, Attention, Action."  "Ask" and "Intention" mean decide exactly what you want (in the positive - if you don't want to be at war, then intend peace) and decide that you will get it - ask for it, intend, it.  "Believe" and "Attention" mean put your focus, attention, and energy on what you want and believe that you can and will achieve it.  Have unwaivering faith that you will get what you asked for.  "Receive" and "Action" mean take any action right now toward achieving your goal, whether it's visualizing and feeling the feelings of having it now, or making a vision board, or starting a new job - the action can be either actual or symbolic, as long as you believe it is a real action toward achieving your goal.

Rhonda Byrnes calls it "The Secret" to sum up all the concepts and to suggest that the successful people in history who knew these concepts, only alluded to them, but did not share them freely with others - they kept it a secret.

"The Secret" tells us, in accordance with scientific findings in quantum physics, that we are not solid pieces of matter as we may appear, but rather we are all made up mostly of energy, and that everything there is, is made of this same energy.  Most religious teachings tell us we were created by God and made in the image and likeness of God, and that God has always and will always exist.  This is also what science, quantum physics, says in different terminology - we are all made from the same energy, and energy can neither be created nor destroyed.  "The Secret" calls this universal energy that makes up everything, God.  So we are all part of God, part of the whole, and we create our own reality, by the Law of Attraction. 

"The Secret" encourages everyone to seek joy, happiness, bliss (note that these feelings/emotions/experiences are distinct from the fleeting, or less meaningful pleasure). When we are happy, we are living up more to our potential, because it is when we are happy that we contribute the most and contribute our best.  (Take a "good deed," for example, like offering a hot meal to someone in need... aren't you more inclined to offer that meal when you feel good, than when you feel bad, and don't you give that person an even greater gift when you offer it with a sincere smile of warmth and joy, than if you offer it with anything less?).  We are meant to be happy and to share our happiness.  While "The Secret" says we can have anything we desire, including material things - it specifically says that material things will not make us happy - we must choose to be happy first, and by being in a state of happiness we will attract more happiness to us.  We can have anything we desire - a beautiful home, a loving relationship, perfect health, etc. and the universe is abundant - there is no lack, the lack is only in our mentality; and not everyone wants the same things!  "The Secret" is about being happy, being positive, being hopeful, and being wealthy in all aspects of life - physically, mentally, emotionally, spiritually, financially.  It's about knowing and understanding your own power and the power throughout the universe - the ability to create the reality we desire because of the fact that we are all connected by one energy.  When we are happy, we serve ourselves, others, and the whole, best.

Jack Canfield says, pretty much everyone's experienced being a victim of some kind - "so what? what are you going to do now?"  Use the Law of Attraction to change the direction of your life for the better right now.  You are in control of your destiny.  When you feel good, you're on the right path, and when you feel bad, you're on the wrong path.

"The Secret" also mentions the "Powerful Processes" of "Visualization" and "Vision Boards".  Search GoodKarma.org for more articles and information on these processes.