Synastry analysis, or chart comparison, is concerned with the actual links between two individual birth charts. It produces an account of the range of ways (physical/sensual, emotional/feeling, mental/thinking, spiritual/soul) two people are likely to interact with each other.
Synastry provides information about how prospective and existing partners will interact emotionally, mentally, sexually, and spiritually. This knowledge can be helpful in understanding and learning to tolerate differences in the way people behave in a relationship. In turn, this helps partners to be more compassionate toward each other, and to adopt more realistic expectations of the relationship. More on Synastry.
Composite, or mid-point charts, are constructed by the melding of two, or more, individual charts. The result is a chart of the actual relationship itself.
Composite charts are suitable for people already engaged in a relationship with a romantic or marriage partner. They reveal the relationship's actual nature and purpose, and how the couple responds to the world. The composite is a representation of what each party to the relationship brings out and stimulates (for better or worse) in the other.
Both approaches can be applied to any important relationship. A friendship, a business partnership, the relationship with a child, a sibling, even a pet - all can be explained with astrological analysis. The chief difference between the two methods mentioned is that a composite chart can be constructed for any number of partners, whereas synastry analysis is restricted to two partners at a time.