A solid understanding of the Model and Paper spaces is crucial when creating drawings in Autocad. This is something which we cover in depth in our Autocad 2d courses. 
Model Space is where most of your drafting work takes place and is accessed via the Model tab; you create all your geometry and models here. The space is three-dimensional and is unlimited, but unless you are working on a 3d model, you would utilize only the x- and y-axes; the z-axis you would ignore. It is as if you are looking down at a drawing placed on the floor. You are in Model Space when you click on the Model tab at the bottom left of the screen. Note the difference between the two User Coordinate System (UCS) icons at the bottom left of the screen: in Model Space it appears as an X-Y axis, and in Paper Space it appears as drafter’s set square. In Model Space you always draw at real-world 1:1 scale, and you decide whether one unit represents 1mm, 1 cm, 1m, 1km, 1 furlong, etc. You do this by going to Application > Drawing Utilities > Units (or pre-2009: Format drop-down menu > Units), or by typing units in the Command line.
Layers and dimensions are generally created in Model space, and any modifications to objects. In contrast to Model space is Paper space. Layout tabs access virtual drawing sheets representing a preview of how the drawing will look when we print. This Layout environment is called Paper Space. A final point is that Model space can be accessed whilst in Paper space by double-clicking inside a Paper space viewport window. We will look at these features in another blog post.
Working with Model and Paper spaces is a crucial part of the Autocad 2d workflow, and we explore them in full in our Autocad classes. You can see many examples of our clients’ work on our Facebook page.
Other related Autocad 2d Blog Posts:

• Autocad 2d basics
• Autocad 2d introduction
• Autocad 2d drawing
• Autocad 2d workspace
• Autocad 2d isometric