  Apparently diffuse X-ray emission has been known to exist along the central
quarter of the Galactic Plane since the beginning of the X-ray astronomy, which
is referred to as the Galactic Ridge X-ray emission (GRXE). Recent deep X-ray
observations have shown that numerous X-ray point sources account for a large
fraction of the GRXE in the hard band (2-8 keV). However, the nature of these
sources is poorly understood. Using the deepest X-ray observations made in the
Chandra Bulge Field (Revnivtsev et al., 2009,2011), we present the result of a
coherent photometric and spectroscopic analysis of individual X-ray point
sources for the purpose of constraining their nature and deriving their
fractional contributions to the hard band continuum and Fe K\alpha line
emission of the GRXE. Based on the X-ray color-color diagram, we divided the
point sources into three groups: A (hard), B (soft and broad spectrum), and C
(soft and peaked spectrum). The group A sources are further decomposed
spectrally into thermal and non-thermal sources with different fractions in
different flux ranges. From their X-ray properties, we speculate that the group
A non-thermal sources are mostly AGNs and the thermal sources are mostly white
dwarf (WD) binaries such as magnetic and non-magnetic cataclysmic variables
(CVs), pre-CVs, and symbiotic stars, whereas the group B and C sources are
X-ray active stars in flares and quiescence, respectively. In the log N-log S
curve of the 2-8 keV band, the group A non-thermal sources is dominant above
about 10^{-14} erg cm^{-2} s^{-1}, which is gradually taken over by Galactic
sources in the fainter flux ranges. The Fe K\alpha emission is mostly from the
group A thermal (WD binaries) and the group B (X-ray active stars) sources.
