quick start

The process of creating and plotting a drawing file in model space is very different from the process used in manual drafting.
In AutoCAD, there are two distinct working environments that are represented by the Model and layout tabs. These tabs are located near the bottom of the drawing area.
If you are going to create a two-dimensional drawing that has one view, you can create both the model and its annotation entirely in model space, not using a layout tab. This is the traditional method for creating drawings with AutoCAD. This method is simple but has several limitations, including
It is suitable for 2D drawings only
It does not support multiple views and view-dependent layer settings
Scaling the annotation and title block requires computation
With this method, you always draw geometric objects at full scale (1:1) and text, dimensions, and other annotation at a scale that will appear at the correct size when the drawing is plotted.
See Also
Create Multiple-View Drawing Layouts (Paper Space)
Work with Sheets in a Sheet Set

contd here