“Metaphysics” is a branch of philosophy that is used to deal with the fundamentals of the nature’s reality like what is it like, how we can understand it, what is ultimately there, etc. It is derived from the sentence “Ta Meta ta Physkia” which means “the books after the books on nature” It helps us to understand the relationship between fact and value, mind and matter, substance and attribute, etc.

For more details you may refer : http://en.wikipedia.org/wiki/Metaphysics