The Fourth House is the bottom of the chart, the foundation upon which everything else is built. It is the house of home, family, roots, and the private life. It describes your childhood home, your relationship with your parents (especially the mother, in traditional astrology), and the inner sense of belonging that sustains you through life.
In traditional astrology, the Fourth House is called the House of Parents (or Fathers, in some traditions — the assignment varies). It describes the quality of your upbringing, the emotional climate of your early environment, and the patterns inherited from your family of origin.
A planet in the Fourth House describes how you experience home and family. The Moon in the Fourth House is at home, giving a deep emotional connection to the family and the home environment. Saturn in the Fourth House often indicates a difficult or restrictive childhood, and a lifelong search for the security that was lacking. Jupiter in the Fourth House gives a warm, generous, and expansive home environment.
The Fourth House is naturally associated with Cancer and the Moon: the sign of home and the luminary of feeling. When planets are placed in the Fourth House, they take on something of this Cancerian quality, becoming more emotional, more protective, more focused on the private world.