You can create and name a layer for each functional category of objects (such as walls or dimensions), and assign it properties to be common to the objects on the layer.
By organizing objects into several layers, you can control the visibility and object properties of a large number of objects separately for each layer, and reduce the visual complexity of a drawing when creating or modifying objects. The number of layers that you can create in a drawing and the number of objects that you can create on each layer are practically unlimited.
The layer names in a drawing are often specified by corporate, industry, or client standards. If you organize your own layer scheme, choose layer names carefully. Use common prefixes to name layers with related drawing components to make it easier to manipulate groups of layers.
If you consistently use a specific layering scheme, you can save time by creating and saving a drawing as a drawing template (DWT) file with layers, linetypes, and colors already assigned. For more information about creating templates, see Use a Template File to Start a Drawing.
As you create objects, they are placed on the current layer. You switch from one layer to another by making a different layer current; any subsequent objects you create are associated with the new current layer and use its color, linetype, and other properties. You cannot make a layer the current layer if it is frozen or if it is an xref-dependent layer.
You can remove unused layers from your drawing with PURGE, or by deleting the layer from the Layer Properties Manager. You can delete only unreferenced layers. Referenced layers include layers 0 and DEFPOINTS, layers containing objects (including objects in block definitions), the current layer, and xref-dependent layers.