There are two types of chart comparison.
The first is a synastry grid, which is a table comparing the Aspects between two charts. This is great for understanding the Karmic needs within any type of Relationship i.e.; Parent/child, Boss/ employee, Friends, Lovers.
The second type of chart comparison is call a Midpoint Composite Chart. This takes the two charts together and forms a third separate chart of the Relationship, NOT the two individuals. This is an advanced chart essential in understanding HOW a relationship will effect to individuals involved. The chart is printed out on a standard wheel format