What are the function of layers in autocad?

Layers are to be able to control manipulate separate parts of the drawings at once with same drawing specifics, of  line types and the way it should appear on the drawing in the end. Things that are the same in type, and you work at the same time them.

Different layers for different things that are similar in group, and you may decide to make a whole layer in a block and use it only it to extract it in other drawing, which otherwise without the layers would be hard to do separately from the rest.

it helps you to organize your project ,it  helps when you need edit your work in short time and if you use layer you can easily make product like the international cad standard.

layer function   help you to  create  categories your drawing objects such as doors , windows ,  lights.... 

initially, we can say that, Layer has more function than a normal paper. we use Layer  to categorize different objects such as wall, doors, etc in architectural and mcbs, wires, lights, etc in electrical. we can us it to define the visibility of the objects too. we can Freeze the layer and we can turn off and on he layers.