Solids
A solid is a collection of surfaces that define a 3D volume. The edges that join faces are shared between the faces. A solid cannot have any holes, for example, a box is a solid, but a box with a missing face is not.
Faces
A face is an individual surface contained in a solid.
Edges
An edge is a curve that connects two faces. These curves are not normally displayed, but you can see them when using dialogs that need an edge.
Sheets
A sheet is a group of surfaces that are created using the solid modeling tools, but that do not create a solid. Sheets have restrictions on how they can be used because they do not enclose a 3D volume. When you create a sheet, a dialog is displayed indicating that a non-solid result was created from the design operation.
