Layers are the equivalent of the overlays used in paper-based drafting. They are the primary organizational tool in AutoCAD LT, and you use them to group information by function and to enforce linetype, color, and other standards.
You can reduce the visual complexity of a drawing and improve display performance by controlling the number of objects that are displayed or concealed. For example, you can use layers to control the visibility of similar objects, such as electrical parts or dimensions. Also, you can lock a layer to prevent objects on that layer from being accidentally selected and modified.
Creating and Listing Layers
Using Layers to Manage Complexity
Changing Layer Assignments and Layer Properties