Need help understanding proportion and scale.

Hi. I'm working on the final project, and am having trouble understanding proportion and scale as it applies to a living room.  Help!!!

The question is this:  "What new design principles have you decided to use? Describe how you will use each principle. Design principles include balance, proportion, scale, and unity."

I think the pieces of furniture I've chosen for the room have good proportions and scale, so I don't know how to answer the questions about them.