A lunar eclipse occurs when the Moon slips into the Earth's shadow. This happens when the Sun, Earth, and Moon are perfectly aligned.
The Moon turns red because the Earth completely blocks direct sunlight. Any light that does reach the moon has been refracted by the Earths atmosphere. This scatters and breaks up the light leaving red. It's the same effect as a sunset.
Starting on November 8th at 1:00 am MST and peaking at 4:00 am MST the Earth will cross between the Sun and the Moon colouring its surface red. Lunar eclipses usually happen a couple times a year but we won't see another here until 2025.
For a quick breakdown of all the details check out this link: