This is the terminology from the Free CAD Lesson Intro to 3D

3D Auto CAD

Terminology

2-D - A concept of displaying real-world objects on a flat surface showing only height and width. This system uses only the X and Y axes.

3-D - A way of displaying real-world object in a more natural way by adding depth to the height and width. This system uses the X Y and Z axes.

Boolean Operations

Commands that allow you to add, subtract or intersect solid objects in AutoCAD.

Complex surface - Generally a curved surface. Examples: car fender, landscape contour.

Elevation - The difference between an object being at zero on the Z-axis and the height that it is above zero.

Extrude - The extrude command raises the shape of a 2D outline into a 3D solid. For example, a circle would be extruded into a cylinder.

Face - The simplest true 3-D surface.

Facet - A three or four sided polygon that represents a piece (or section) of a 3-D surface.

Hidden line removal - A way of hiding lines that would not be visible if you were viewing the actual object you have drawn in AutoCAD. (Command: HIDE)

Isometric Drawing

A simple way of achieving a '3-D' appearance using 2-D drawing methods.

Plan View - Also known as the top view, a plan view looks directly down the WCS Z-axis to the X-Y axis.

Primitive

A basic solid building block. Examples would be boxes, cones, cylinders.

Region

A 2-D area consisting of lines, arcs, etc.

Rendering

A complex way of adding photo-realistic qualities to a 3-D model you have created.

Shading - A quick way of adding color to a 3-D object you have drawn. (Command: SHADE)

Solid Model - A 3-D model creating using solid 'building blocks'. This is the most accurate way of representing real-world objects in CAD.

Surface Model - A 3-D model defined by surfaces. The surface consists of polygons. (See facets.)

Thickness

A property of lines and other objects that gives them a 3-D like appearance.

USC

The user co-ordinate system. This is defined by the person drawing to have easier access to portions of a 3-D model.

View

A particular view of the object you have created.

Viewport

A window into your drawing showing a particular view. You can have several viewports on your screen. Different from the viewports used in plotting.

Wireframe Model

A 3-D shape that is defined by lines and curves. A skeletal representation. Hidden line removal is not possible with this model.

Z-axis

The third axis that defines the depth.