The law of attraction simply states that what we focus upon is attracted onto our reality. If we focus on the positive aspects of our reality, we will attract more of it. On the other hand, when we focus on the negative aspects of our reality, our life will become full of new and bigger negative characteristics, events and experiences.
This is a rather simplistic definition, which in my opinion is the source of a great deal of confusion.
In order to really understand what the law of attraction is, first we must understand of what is composed.