What Is Natal Astrology?
Traditional vs Modern
Traditional astrology tried to gain a lot of information from reading the subject's birth chart. A belief in predestination led to an attempt to predict almost everything about the subject's life in detail: marriage, illnesses, major events, etc.
Today such a rigid interpretation of the chart is no longer popular. Instead the chart is more frequently used to give a feeling for a person's overall character and the general tendencies of their life. It's a higher level, more holistic approach.
There are other ways to use the birth chart. For example two individual charts can also be combined for compatibility analysis. Or a birth chart can be combined with a chart on a particular day for more in depth prediction. Although both of these use the birth chart, astrologers vary as to whether or not they should truly be called natal.