About Composite Surfaces
A surface that contains at least one composite chain as a boundary or internal curve is a composite surface. The composite chain can consist of different types of curves, but they must join at the ends with tangent or curvature continuity. Composite surfaces are composed of a set of surfaces but are treated as a single entity. Outside Style, such surfaces are treated as a single quilt. The surface normals of the component surfaces are oriented consistently with each other.
During creation or redefinition, you can convert any type of Style surface, boundary, loft, or sweep, to another type by selecting a different set of boundary chains.