Since the first detection of gravitational wave (GW) in 2015, a term called multi-messenger astronomy (MMA) has emerged and drawn great public attention. MMA covers both traditional electromagnetic (EM) and non-electromagnetic observation such as GW, neutrino, and cosmic-ray although multi-wavelength EM observation could be called MMA in a narrower sense. In this colloquium, I will deliver some basic knowledge for MMA, focusing on neutrino astronomy, with my own perspective. I will also introduce some efforts to construct a neutrino telescope within Korea and present some recent studies of the UNIST group that estimate detectability of some astrophysical neutrino sources.