Eclipse
An eclipse is a New or Full Moon that falls close enough to a lunar node for the three bodies to line up, so a solar eclipse hides the Sun and a lunar eclipse darkens the Moon.
The nodes are why eclipses come in seasons rather than at random. They can only happen when a lunation lands near the intersection of the Moon's orbit with the ecliptic, which occurs about every six months and moves slowly around the zodiac.
Classical eclipse doctrine belongs to mundane astrology, written about states and rulers, and its tone is far gloomier than modern personal practice. Read in a birth chart, an eclipse marks the house it falls in as being in season, which is a description of emphasis rather than a prediction.
Frequently asked
Why do eclipses come in pairs?
Because an eclipse season lasts about a month, long enough for both a New and a Full Moon to fall near the same node.
How do I read an eclipse in my own chart?
Find the house that holds its degree. The house names the area of life, and a solar eclipse reads as an opening where a lunar one reads as a culmination.