Shapes are composed of faces, edges, and vertices. Faces enclose a solid volume. Faces have three or more edges that surround its perimeter. Edges have two vertices. For example a Box shape has six faces, and each face has four edges but those edges are shared by faces so the Box has 12 distinct edges in total. Each edge has two vertices but these are also shared so the Box has eight distinct vertices in total.
Since all pieces of a Shape are solved together as a single shape unit, once a shape is solved by marking enough edges (e.g. you mark 7 edges of the shape), the 3D model will have the fully solved shape (i.e. the shape will include the edges not marked and the faces not seen).