What is a solar eclipse?

A solar eclipse occurs when the Moon passes in front of the Sun by masking it, this produces an effect of darkening the sky.
There are several types of solar eclipses :

Total solar eclipse

During a total solar eclipse, the moon completely masks the sun (apart from its crown). The night becomes visible in broad daylight for about 8 minutes.

Annular eclipse

During an annular eclipse, the Sun, the Moon and the Earth are perfectly aligned but the size of the Moon (caused by the variation of its distance from the Earth) is slightly smaller than that of the Sun which reveals a brilliant ring around the moon.

Partial solar eclipse

During a partial eclipse, the Sun and the Moon are not perfectly aligned and the moon only hides part of the Sun.

Although the Sun is much larger than the Moon, the Sun is also at a much farther distance from the Earth than the Moon is and therefore, from the point of view of the Earth, the Sun and the Moon have diameters that are close together, which means that during its passage in front of the Sun, the Moon masks it.
Indeed, the Sun is about 400 times larger than the Moon, and the distance between the Earth and the Sun is 390 times greater than that between the Earth and the Moon.