Question

what is eclipse and write it's reaction on planets

Answer 1

The many eclipse phenomena known to astronomers are of two distinctly different types. In the first, the eclipsing body comes between an observer and the eclipsed object; the latter appears to the observer totally or partly covered by the eclipsing object. Eclipses of the Sun, occultations of stars by the Moon, transits of Venus or Mercury across the Sun's disk, and eclipses of binary stars are of this kind. Eclipses of the second type affect only planets or natural satellites that are not self-luminous. In this case, the eclipsing body intervenes between the Sun and the eclipsed object. The latter remains in view of the observer, but its illumination by the Sun is interrupted, and it becomes darkened by entering into the shadow of the eclipsing object. Examples of this kind of eclipse phenomenon are eclipses of the Moon.

Answer 2

An eclipse is the result of either an occultation or a transit. The term eclipse is most often used to describe either a solar eclipse, when the Moon's shadow crosses the Earth's surface, or a lunar eclipse, when the Moon moves into the Earth's shadow