Active Model Space
Model may be edited in model space.
Tiemode = 1 (on)
All drawing done in model space should be 1:1.
Active Paper Space
Title block or other non-model space information may be edited in the paper space viewport.
Tiemode = 0 (off)
When tilemode is off viewports are objects that can be moved and resized.
Paper Space with Active Model Space Viewport
To enter the viewport, type ms at command line : note the model space icon.
Tilemode = (off).
Paper space scales (XP) may be set by zooming while in this mode. Editing of the model is possible though not encouraged