A drawing can contain multiple layouts (sheets): the Model Space layout which usually contains the model representation and a few Paper Spaces (printable sheets) which represent paper space and are usually used for laying out the drawing for printing.

Paper Space can contain viewports which display the contents of Model Space and some (usually 2d) entities representing borders of the drawing, annotations, etc. A number of viewports with different settings can display contents of Model Space in Paper Space with different view directions, scales, etc. For example, a top view, left view, or isometric view of the model on the same sheet.