  A synthesis of the present knowledge on gamma-ray emission from the
magnetosphere of a rapidly rotating neutron star is presented, focusing on the
electrodynamics of particle accelerators. The combined curvature, synchrotron,
and inverse-Compton emission from ultra-relativistic positrons and electrons,
which are created by two-photon and/or one-photon pair creation processes, or
emitted from the neutron-star surface, provide us with essential information on
the properties of the accelerator -- electric potential drop along the magnetic
field lines. A new accelerator model, which is a mixture of traditional
inner-gap and outer gap models, is also proposed, by solving the Poisson
equation for the electrostatic potential together with the Boltzmann equations
for particles and gamma-rays in the two-dimensional configuration and
two-dimensional momentum spaces.
