Setting the layer state to thaw or freeze a layer is very similar, visually, to turning a layer on or off.
For example, you could use the tools in the Layer drop-down to turn off the FURNITURE layer. When that layer is turned off, you no longer see the objects on that layer. The layer is still there, but its objects are no longer visible. When you turn the layer on again, its objects are once again visible.
In the Layer drop-down, if you click the Freeze tool, the affect on-screen is very similar-the objects on that layer are no longer visible. But there is a difference, because when a layer is frozen, the objects on that layer are no longer included in any display calculations when you zoom or pan, which can make zooming and panning faster when working in a large drawing.
In most cases, you may turn layers on and off frequently to control the visibility of objects. But if you do not need to see the objects on a particular layer for an extended period of time while working on a drawing, freeze the layer to improve the overall performance.
There is also one other difference between freezing a layer and simply turning it off. If you attempt to turn off the current layer, the program will ask if you really want to do this, and it is possible to turn off the current layer. But you cannot freeze the current layer. If you attempt to freeze the current layer, the program will display a warning telling you that you cannot freeze the layer because it is the current layer. The program will not allow you to freeze the current layer.
Source: Autodesk
