What exactly is a birth chart or horoscope?

On an empirical level, the birth chart is a "not drawn to scale" representation of the planets, astrological houses, and zodiacal signs in relation to each other from the perspective of earth at the precise moment of birth. For the sake of clarity, certain physical relationships in the birth chart are emphasized and kept accurate—the angular relationship between the planets, for instance—while other factors are ignored or de-emphasized—the scale of distance between planets. When one becomes aware of what is truly being mapped in an astrological birth chart, it suddenly dawns that an astrological birth chart and a Sun Sign horoscope are two different animals entirely; the birth chart is a complex modeling of a blending of actual physically observable things—planets—with centuries-old projected constructs—houses and signs. It is often difficult for a student or client to enter into an astrological chart because of the level of abstraction that is going on, the collapsing of three dimensions into a two-dimensional surface, and the unfamiliar symbolism that populates the chart.