What is an eclipse and how does it happens?

Answer 1

An eclipse is a blocking; something is "eclipsed" meaning that our view of it is blocked.

In astronomical terms, an "eclipse" is when the Sun's light is blocked, and a shadow falls on another object. In a solar eclipse, the Moon does the blocking, and the Moon's shadow falls on the Earth; the Sun is "eclipsed", and the Sun's light is blocked.

In a lunar eclipse, the Earth does the blocking, and the Earth's shadow darkens the Moon. Because the Earth is so much larger than the Moon, the shadow of the Earth can completely darken the Moon when the Moon's orbit passes through the shadow of the Earth.

There are generally two solar eclipses and two lunar eclipses each year.

Answer 2

an eclipse is when there is a perfect allingment with the moon and sun, causing the moon to go over the sun and everything becomes black.