There are two major definitions of metaphysics. The first refers to a branch of philosophy concerned with the nature of reality, mind, matter, truth, time, identity, and God. This branch of philosophy was started by Aristotle with his book "Metaphysics", or "After Physics", which followed his book titled "Physics".
The second definition of metaphysics refers to that which is beyond the physical, or that which deals with the interaction between mind and matter. This includes the metaphysical arts such as psi, qi gong, and magick, and includes spirituality and mysticism.