What is meant by "low relief" structures

I finally got my Feb MR today and I found a manufacturer selling low relief buildings. Just what are these structures?
BB

It means that it is not fully modeled in terms of depth
The building is scale height and length but is shallow, so that it can be placed against a backdrop. This is opposed to a flat, which is literally just that: just a side with no roof and no depth at all.
Most low relief structures are just an inch or two deep. So it sticks out from the backdrop but is not full scale depth.
Dave Nelson

Low relieve buildings are buildings that are not modeled in their entirety. Low Relief buildings are buidings that are cut down and are meant to be mounted up against the back drop. This allows a modeler to model a rather complex and large industry and focus on railroad operations of that industry but not use up valuble acres of model railroad realestate. There are other low reliefe sructures that are meant to add atmospher and add a touch of civilcation trackside.

James