Layers are really useful when you have added a great many objects to your drawing. Think of layers as sheets of tracing paper, which were pretty common in the hand-drafting days. We can draw different parts of a project on different sheets of tracing paper – you could have one sheet of tracing paper for the walls of a house, then another one for the internal furnishings of the rooms, and then another one for the dimensions. Then, we could overlap these sheets of tracing paper to get the complete house plan, and if we needed to show the drawings without any particular properties, such as dimensions, then we could simply remove the dimensions sheet from the project.
Layers in AutoCAD work in pretty much the same way, but in this case, it's obviously much more powerful and feature-packed than traditional tracing paper. In the drawing shown...
