A lunar eclipse is an astronomical phenomenon. It happens when the moon passes through the shadow of the Earth which can only occur during a full moon. Lunar eclipses happen about twice a year and can be seen from a much larger portion of the Earth compared to solar eclipses. Lunar eclipses can last for a few hours, but solar eclipses may last only a few minutes.
During a lunar eclipse, the Moon looks red-brown. It may be thought that the Moon is completely black because of the Earth's shadow, but no. The reddish-brown color is because some of the Sun's light bends through the Earth's atmosphere and shines on the Moon. Refraction is greater for red light rays than for others, so red is what strikes the Moon.
Like solar eclipses, there are different types of lunar eclipses. There are total eclipses, where the moon passes completely through Earth's shadow and all of the moon appears reddish-brown. A partial eclipse occurs when only part of the moon passes through Earth's shadow and so only part of the moon appears reddish-brown.
Lunar eclipses are safe to view with just your eyes and also with telescopes.