The Model tab accesses a limitless drawing area called model space. In model space, you draw, view, and edit your model.
In model space, you draw your model at 1:1 scale, and you decide whether one unit represents one millimeter, one centimeter, one inch, one foot, or whatever unit is most convenient or customary in your business.
On the Model tab, you can view and edit model space objects. The crosshairs cursor is active over the entire drawing area.
In model space, you can also define named views that you display in layout viewports on a layout.