I am using Home Designer Architectural. 
  
I have used layers in many other programs, but I am having trouble understanding how Home designer layers work. 
  
I have 2 terrain features that overlap.  Since they are terrain features, I think they are considered to be on the same layer, but they don't act like it.  I put in a terrain feature of a cobblestone area and later put in a terrain feature of just ground cover that I wanted underneath the cobblestone feature.  That is the way it turned out, but I don't understand why.   
Usually in the other graphic programs I have used, the last item entered went on a layer that covered the previous item that was on a layer below and if you wanted to change it, you would have to reorder the layers.  How do I determine the layer (or more probably the order) of what is on top of what?  Is there a video, discussion, webinar or something that reviews this and makes this clearer?