  We present an overview of angle-resolved photoemission spectroscopy (ARPES)
studies of high-temperature cuprate superconductors aiming at elucidating the
relationship between the superconductivity, the pseudogap, and the Fermi arc.
ARPES studies of underdoped samples show a momentum dependence of the energy
gap below Tc which deviates from a simple d-wave form, suggesting the
coexistence of multiple energy scales in the superconducting state. Hence, two
distinct energy scales have been introduced, namely, the gap near the node
(characterized by Delta_0) and in the anti-nodal region (characterized by
Delta^*). Dichotomy between them has been demonstrated from the material,
doping, and temperature dependence of the energy gap. While Delta^* at the same
doping level is approximately material independent, Delta_0 shows a strong
material dependence tracking the magnitude of Tc,max. The anti-nodal gap does
not close at Tc in contrast to the gap near the node which follows something
closer to a BCS-like temperature dependence. An effective superconducting gap
Delta_sc defined at the end point of the Fermi arc is found to be proportional
to Tc's in various materials.
