Horizontal Axis -- the Ascendant
The horizontal axis represents the horizon line at the time a chart is cast. In a birth chart it is the very first viewpoint that newborn perceives. The fact that no two people are born at the exact same place and time is the reason that everyone has an individual personality astrologically. The point on the left side of the horizontal axis is called the Ascendant. The astrological sign on the ascendant is called the Rising Sign, which shows how you present yourself to the world; where the sun sign represents your inner drive and character, the rising sign shows your façade. Some people have the same rising sign as sun sign, and do not appear to be secretive about themselves.
Horizontal Axis -- the Descendant
The right end of the horizontal axis is called the Descendant. In a birth chart, the point and sign indicate how you relate to the world through your partner, who may be a spouse or business partner. It also indicates the character of the person you will choose for a partner.
Vertical Axis -- the Midheaven
The vertical axis shows how the sky appeared directly overhead when you were born. It represents the most outward expression of your personality. The topmost point is called the Midheaven. It indicates the career that you will be the most satisfied performing. When transiting or progressed planets come in contact with the Midheaven, you usually feel a shift of their position in life. The person most often associated with the Midheaven is the one who helped show you how to act in the world outside of the home -- usually the father figure.
Vertical Axis -- the Nadir
The nadir is the lowest point of the chart. The sign on it shows how you establish your root system. It indicates what your home will be like. The person most associated with the nadir is the one who nurtured you as a child, usually your mother. When transiting or progressed planets come in contact with your nadir, you may make changes to your home.