As we've seen from the replies you've had so far, "Mind Power" means different things to different people, and in different contexts.
On a Practical level, "setting your mind" to something can help you achieve a task you may otherwise have not been able to handle is one interpretation...
On a Spiritual level, there are many interpretations and uses for the mind - including, as Sharon mentioned, the Law of Attraction; as well as, psychic abilities, sensitiviy, and the power of meditation etc.
On a Quantum level, (apart from the Law of Attraction - which has a quantum base as well as a spiritual one) there is the ability to affect physical matter with the Power of the Mind. One source of this Power of the Mind, is demontrated in experiments conducted by Princeton University, which you can read about here: Princeton University PEAR Project
A quote from the website, on the results of the project:"The enormous databases produced by PEAR provide clear evidence that human thought and emotion can produce measureable influences on physical reality."
Also in the Quantum field, there is the Power of the Subconscious mind to connect with the Collective, resulting in Synchronicities.
The Power of the Mind over Bodily Functions is also interesting. The Subconscious controls around 90% of our bodily functions, and people are able to adjust "unconscious" bodily functions (heart rate, body temperature, and/or immune system for example), by consciously intending this. If the person is able to communicate this conscious intention to the Subconscious mind, which controls that function, then the body responds accordingly.
Mind Power, particularly in its Spiritual and Quantum interpretations, is one of my favourite subjects.
Love and Light and Magic xxx