What is an eclipse of the sun? To know more about it, it is necessary to talk about the moon first.

Phases of the Moon
The moon is a cold, rocky body about 2,160 miles (3,476 km) in diameter. It has no light of its own but shines by sunlight reflected from its surface. The moon orbits the earth about once every 29 and a half days. As it circles our planet, the changing position of the Moon with respect to the Sun causes our natural satellite to cycle through a series of phases:
New Moon > New Crescent > First Quarter > Waxing Gibbous> Full Moon > Waning Gibbous > Last Quarter > Old Crescent > New Moon (again)
The phase known as New Moon can not actually be seen because the illuminated side of the moon is then pointed away from the earth. The rest of the phases are familiar to all of us as the moon cycles through them month after month. The New Moon phase is uniquely recognized as the beginning of each calendar month just as it is the beginning on the moon's monthly cycle. When the Moon is New, it rises and sets with the sun because it lies very close to the sun in the sky. Although we cannot see the moon during New Moon phase, it has a very special significance with regard to eclipses.

The Moon's Two Shadows
An eclipse of the sun (or solar eclipse) can only occur at New Moon when the moon passes between the earth and the sun. If the moon's shadow happens to fall upon the earth's surface at that time, we see some portion of the sun's disk covered or 'eclipsed' by the moon. Since New Moon occurs every 29 1/2 days, you might think that we should have a solar eclipse about once a month. Unfortunately, this doesn't happen because the moon's orbit around the earth is tilted 5 degrees to the earth's orbit around the sun. As a result, the moon's shadow usually misses the earth as it passes above or below our planet at New Moon. At least twice a year, the geometry lines up just right so that some part of the moon's shadow falls on the earth's surface and an eclipse of the sun is seen from that region.
The moon's shadow actually has two parts:
1. Penumbra
The moon's faint outer shadow.
Partial solar eclipses are visible from within the penumbral shadow.
2. Umbra
The moon's dark inner shadow.
Total solar eclipses are visible from within the umbral shadow.

Never observe directly any other solar phenomenon, e.g., the transits of the planets Venus and Mercury. Unfortunately, every year there are several cases of people who suffer retinal burns because of looking directly at the sun without protecting their eyes. In Egypt, some people suffered retinal burns as they viewed the total solar eclipse of 11 August 1999 (which was partial in Egypt ) without protecting their eyes. There are even recorded cases of people who lost eyesight because of staring at partial eclipses of the sun.

A solar eclipse is a fascinating experience that is not to be missed. To better observe a solar eclipse safely, you can use the pinhole cameras, the sunspotters and refractor telescopes. They are the safest way for you.