During a lunar eclipse, Earth comes between the Sun and the Moon, blocking the sunlight falling on the Moon.
During some stages of a lunar eclipse, the Moon can appear reddish. This is because the only remaining sunlight reaching the Moon at that point is from around the edges of the Earth, as seen from the Moon's surface. From there, an observer during an eclipse would see all Earth's sunrises and sunsets at once.
The Jan. 31 full Moon (which will also be a supermoon) will feature a total lunar eclipse, with totality viewable during the early morning hours from western North America across the pacific to Eastern Asia.