Glossary/Drawing basics
Model space
The full-scale drawing environment where the actual design geometry lives.
Model space is where you draw the real thing — a pipe run, a floor plan, a part — at true (1:1) scale. Every drawing has exactly one model space, and it's the default view AutoCAD opens into.
Layouts (paper space) reference model space through viewports to compose what actually gets printed, at whatever sheet scale is appropriate — the geometry itself isn't redrawn or duplicated for each sheet.