As the earth and moon revolve in their respective orbits, sometimes they will block each other's sunlight creating shadows. The moon gets between the earth and sun or the earth gets between the moon and the sun. In either case you will experience an eclipse. If the earth is blocking the light from the sun we will have a Lunar Eclipse. If it is the moon blocking the sunlight then we will experience the Solar Eclipse.
This occurs when the earth moves in between the moon and sun and forms a straight line. The earth blocks the light from the sun creating a shadow and the moon moves into this shadow. A reminder that the moon has no light; it reflect light. Since it is in a shadow, it does not receive any light to reflect so this results in the moon becoming very dark. Normally, the moon will not become really dark because the earth's atmosphere will scatter and bounce the light back towards the moon. The amount of dust and particles in the atmosphere affects the colour you see. Very often it appears to be a deep orange or copper colour. This will happen one or two times a year during a full moon. This eclipse can be seen from anywhere in the world as long as the moon happens to be in the sky at the time.
penumbra - outer part of the shadow, sunlight is not completely blocked
umbra - is the actual shadow, all light lost
Types of Lunar Eclipses
Let's try a little experiment. We will start off with making your head the earth. Behind you the sun is shining brightly. The earth ( your head ) is blocking some of the light causing a shadow to appear. That is shown above as the penumbra and umbra. Now here comes the moon in its orbit. It passes in front of you ( earth ) and goes right into the shadow that you have made. If the moon goes into just the penumbra than that is the Penumbra LunarEclipse. - fig 1. If the moon 's orbit takes it through both the penumbra and the umbra at the same time, as in fig 2, then it is a Partial Lunar Eclipse. In fig 3, we have a Total Lunar Eclipse. The entire moon moves right into the darkest part of the shadow, the umbra. There you have it.
The Solar Eclipse is not as common as the Lunar Eclipse. It can only take place during a New Moon and only when the earth, moon and sun line up in a straight line. The New Moon must be between the earth and the sun. The shadow is cast upon the earth this time. Again, there are the two shadows; the penumbra and the umbra. If the sun is totally blocked from our view by the moon then we experience a Total Eclipse. We would be in the umbra. If the sun is partially blocked, then a Partial Eclipse occurs. This happens in the penumbra. Now, depending on where you are living, you may experience a total eclipse or you may have the partial eclipse.