Layer

Layers help to organize objects in the drawing, and enforce properties like color, linetype and lineweight standard

You can create chair, desk, cabinet on the furniture layer
When you change the color of the furniture layer, all objects on this layer will follow

Default Layer

By default, every new drawing will automatically create a 0 layer

You cannot rename or delete the default layer
Layer 0 use to establish predictable behaviors fro objects like blocks

Layer Properties Manager

Home tab > Layer panel > Layer Properties

You can create unlimited layers, and assigned properties
Only 3 properties need to be assign when creating layers, they are Color, Linetype, Lineweight