  In the first and second post-Newtonian approximation of the Schwarzschild
metric, I obtain the energy component of the Einstein and M{\o}ller
energy-momentum complex. Both energies involve the rest-mass energy $m$, the
energy stored in the configuration and that in the gravitational field, but the
energies of Schwarzschild spacetime in the Einstein and M{\o}ller prescriptions
are the total mass-energy $M$. First, for general relativity, the rest-mass
energy $m$ in the flat spacetime behaves like the bare mass, and the total
mass-energy $M$ in the curved spacetime behaves like the experimentally
observed mass. Second, the zero-potential surface is important condition for
defining the energy of gravitational field, and plays an important role in the
energy-momentum localization of general relativity.
