On August 21, 2017, a 121-mile wide shadow will sweep across North America as millions of people revel in a total solar eclipse — the first one to run from sea to shining sea since 1918. Earth's shadow is red at the edges which is also the same as a sunset is red: When sunlight is blocked by passing through Earth's atmosphere, or in other words its blanket of gas, the other colors are removed. In a solar eclipse, the moon casts its shadow on Earth. And in other hand the eclipse blocs an object on space and the shadow of that is what we get to see here in Earth.
The moon's shadow casts on the Earth, resulting in solar eclipse. Lunar eclipses are only possible to occur during a full moon and when the moon is on the ecliptic plane. Only during full moon, the Sun's light rays will be blocked.So in other words, an eclipse is when one object in space blocks the possibility from seeing another object in space.