Moon
The Moon governs emotions, habits and the need for security. Its sign often describes a person more accurately than the Sun sign, especially how they are at home and under stress.
Governs
The Moon shows what a person needs in order to feel okay: what surroundings, what rhythm, what kind of care. It also governs the first, involuntary reaction, before conscious choice kicks in.
Traditionally, the Moon is associated with the mother, childhood, home, food and bodily habits. Its cycle through the signs is about 27.3 days (and from new moon to new moon, 29.5), and it changes sign roughly every two and a half days, so without a birth time the Moon sign sometimes cannot be determined.
In the signs and houses
The Moon sign sets your emotional style: a Scorpio Moon feels things deeply and silently, a Gemini Moon talks everything through out loud. You can find your Moon sign and read its interpretation with the Moon Sign calculator.
The Moon's house shows where a person seeks security: in the fourth, at home; in the tenth, in status and recognition.
You can look up the Moon’s phase for any date in the lunar calendar — anyone can check the phase simply by looking at the sky; the interpretations, however, remain a matter of tradition.
Strong and weak placements
Domicile: Cancer; exaltation: Taurus. Detriment: Capricorn; fall: Scorpio.
The Moon is the fastest point in the chart, which is exactly why "daily" horoscopes are most often based on it: it manages to change sign in a couple of days and creates the feeling that the forecast has been updated.