The Moon represents the inner world: your emotions, your emotional needs, what reassures or worries you without you needing to think about it. The sign it occupies describes your instinctive way of reacting and feeling secure.
It is often the most recognizable planet day to day: the Sun is what you consciously aim to become, the Moon is what you already are, spontaneously, especially in private.
Domicile: Cancer. Exaltation: Taurus. Detriment: Capricorn. Fall: Scorpio. The Moon is the nocturnal luminary — it takes on the Sun's diurnal role in a chart born at night.
Its phase (new, waxing, full, waning…) at the moment of birth qualifies the overall momentum of the chart: a waxing Moon evokes a movement being built, a waning Moon a movement being closed out and digested.
The Moon finds its joy in the 3rd house (close surroundings, daily exchanges, short trips).