An eclipse is an astronomical event defined by the temporary obscuration of one celestial body by the shadow of another. These phenomena primarily occur due to the predictable alignment of three or more massive celestial bodies. The most observable types involve the Sun, Earth, and Moon. A solar eclipse occurs when the Moon passes between the Sun and Earth, casting its shadow onto a portion of the Earth's surface. Conversely, a lunar eclipse happens when the Earth passes into the shadow cast by the Moon, resulting in a darkening or reddening of the lunar surface. The occurrence and nature of these events are governed by the mechanics of orbital geometry and the relative distances and orbital planes of the involved bodies.