Layers Help

I am working through the book "Learning 2D Game Development with Unity" and continue to find issues I am struggling with. The book tells me to create 4 layers under "SORTING LAYERS" and then I can use that to assign a layer to my game objects. I have done this but "sorting" layers dont show up in the inspector for game objects, only layers do so I can not assign these sorting layers to my game objects. I am trying to place a fence in the foreground so my player will walk behind it

Can someone explain what the difference between "sorting" layers and "layers" is?

Should I just create my layers under layers and forget what the book says on this so I can assign them to objects?

How do I assign a sorting layer to a game object?

 

Layers:
Background organizational identifier for an object, like "Enemies" layer, or "Props" layer.

Sorting Layers:
What order things are rendered.

 

So a "layer" is just an identifier to keep things grouped while the "sorting layer" is used to place objects in front of and behind the player?

 

Basically, yeah.

 

I use a "layer" to decide what is going to collide with each other within the 2d physics settings and things of that nature rather than as an identifier. I use tags for identifying purposes.

 

"Layers" can also be used by the camera to decide what's visible to that camera and what is not.