is used to create the base 2D profiles for creating solid models, surfaces, and T-spline forms. It's the 2D geometry that supports the creation of the 3D part.

creates T-Spline, solid, or surface revolved features by sweeping sketch and model geometry around an axis.

a cad object defined by two endpoints

Creates a 3D solid or surface by specifying a series of cross sections. The cross sections define the shape of the resulting solid or surface. You must specify at least two cross sections.

part of a circle you can connect by two points. You can specify combinations of center, endpoint, start point, radius, angle, chord length, and direction values.