Fitra is the original state of spiritual health in which humans are created by God. The commonly accepted meaning of this word derives from the traditions of Muhammad. It describes the original pure state in which God creates each of us. Something quite different from the concept of original sin, which does not exist for muslims.
As such, every child is born not only pure, but muslim, which simply means "surrendered to God." A child's parents, depending upon their culture, might then raise her or him to believe differently or behave in some other manner. But we are originally created in a pure state by God. And in service to our creator.
So our original nature is one of spiritual health, of moral beauty, and of surrender to God.
This concept of fitra ~ the original healthy constitution of each human being's nature as created by God ~ is invoked by sufis, who view their own quest as a means for restoring or rediscovering the original beauty of our own nature, in harmony with that of creation, as servants of the Creator.