  We review current understanding of kilonova/macronova emission from compact
binary mergers (mergers of two neutron stars or a neutron star and a black
hole). Kilonova/macronova is optical and near-infrared emission powered by
radioactive decays of r-process nuclei. Emission from the dynamical ejecta with
~0.01 Msun is likely to have a luminosity of ~10^{40}-10^{41} erg s^{-1} with a
characteristic timescale of about 1 week. The spectral peak is located in red
optical or near-infrared wavelengths. A subsequent accretion disk wind may
provide an additional luminosity, or an earlier/bluer emission if it is not
absorbed by the precedent dynamical ejecta. The detection of near-infrared
excess in the afterglow of short GRB 130603B and possible optical excess in GRB
060614 supports the concept of the kilonova/macronova scenario. At 200 Mpc
distance, a typical brightness of kilonova/macronova with 0.01 Msun ejecta is
expected to be about 22 mag and the emission rapidly fades to >24 mag within
~10 days after the merger. Kilonova/macronova candidates can be distinguished
from supernovae by (1) the faster time evolution, (2) fainter absolute
magnitudes, and (3) redder colors. To effectively search for such objects,
follow-up survey observations with multiple visits within <10 days and with
multiple filters will be important. Since the high expansion velocity (v ~
0.1-0.2c) is a robust outcome of compact binary mergers, the detection of
smooth spectra will be the smoking gun to conclusively identify the GW source.
