Strictly defined, a solar eclipse is what happens when the moon comes between the sun and the Earth, blocking part or all of the light from the sun. (A lunar eclipse happens when the Earth passes between the moon and the sun.) A solar eclipse can be total, partial or annular, and it can be seen only for a short period of time from a certain part of Earth. A total eclipse, which happens once every year or two, occurs when the moon entirely blocks out the sun.
Pictured here is a total eclipse that happened on Dec. 3, 2002, as seen from Australia — the first solar eclipse for that country since 1976. According to NASA, "... people in Australia received a rare 32-second celestial show as the moon completely obscured the sun, creating a ring of light. ... This image combines a photograph of the solar eclipse (showing the halo-like corona) with data taken by the Extreme Ultraviolet Imaging Telescope instrument aboard SOHO (showing the green inner regions)."