What is Layer 0 and Layer Defpoints in autocad?

[lora]

Just wondering the purpose or intent of these layers? Do they have any additional features when compared to any other layer that I might create on my own? Is there some standard info that others may expect to find on these layers when I begin sharing my drawings with customers or suppliers?

[ok]

Layer "0" is just a default layer. The caveat has always been to not put anything on layer 0. It is also said that this is the layer one should create blocks on so that upon insertion into other layers the blocks will assume the properties of the layer (color, linetype, etc.). Of course most newbies draweverything on layer 0 and then compound the error by overriding settings for color and linetype thus creating headaches for others who know better. When I receive a drawing like this from an outside source I know it is going to be a long, long day and I break out the large bottle of aspirin.