  This short document is intended as a companion and introduction to the
Detailed Science Case (DSC) for the Maunakea Spectroscopic Explorer. It
provides a concise summary of the essential characteristics of MSE from the
perspective of the international astronomical community. MSE is a wide field
telescope (1.5 square degree field of view) with an aperture of 11.25m. It is
dedicated to multi-object spectroscopy at several different spectral
resolutions in the range R ~ 2500 - 40000 over a broad wavelength range (0.36 -
1.8{\mu}m). MSE will enable transformational science in areas as diverse as
exoplanetary host characterization; stellar monitoring campaigns; tomographic
mapping of the interstellar and intergalactic media; the in-situ chemical
tagging of the distant Galaxy; connecting galaxies to the large scale structure
of the Universe; measuring the mass functions of cold dark matter sub-halos in
galaxy and cluster-scale hosts; reverberation mapping of supermassive black
holes in quasars. MSE is the largest ground based optical and near infrared
telescope in its class, and it will occupy a unique and critical role in the
emerging network of astronomical facilities active in the 2020s. MSE is an
essential follow-up facility to current and next generations of
multi-wavelength imaging surveys, including LSST, Gaia, Euclid, eROSITA, SKA,
and WFIRST, and is an ideal feeder facility for E-ELT, TMT and GMT.
