When this happens, the moon can obscure the entire sun or part of it from view, casting a shadow on the Earth and making it appear as though the sun has darkened. This phenomenon can only occur during a new moon phase, when the sun and the moon are in conjunction as viewed from Earth.

In a total solar eclipse, the disk of the sun is fully obscured by the moon. However, in partial and annular solar eclipses, only part of the sun is obscured. If the moon were in a perfectly circular orbit, a little closer to the Earth, and in the same orbital plane, there would be total solar eclipses each new moon. However, the moon's orbit is inclined at more than 5 degrees to the Earth's orbit around the sun so its shadow at new moon usually misses Earth.

Solar eclipses are relatively brief events that can be viewed in totality only from a narrow track on the surface of the Earth. Observers outside this path will still see a partial solar eclipse where the moon covers only a part of the sun's disk. Eclipses of some sort are almost monthly phenomena due to the orbits of the earth and the moon.