Sounds ominous, doesn't it? Well, a marshalling yard is not a place that should fill you with fear; it's a place that should fill you with confidence. It's simply a lot where trucks gather for orderly dispatch to a trade show site.
This describes a large set of sidings used to marshall trains, i.e. put together wagons which are all going to the sme destination into one train. Often such a yard will have an Up side and a Down side. Before entering the main set of sorting sidings there will probably be reception sidings - these are used to hold an arriving train until the yard is ready to split it up and combine it with other wagons for dispatch.