Some families set aside large amounts of space in basements or recreational rooms to house elaborate railroad displays, with tiny villages, trees, figurines of people and animals, and other scenery. It is possible to buy scale models of engines, railroad cars, and other components, or they can be built from kits. Buying the models can be quite expensive. There are several basic sizes of model railroads. The size depends upon the scale and gauge.
Scale is the proportional reduction from full size to model.
Gauge is the distance between the inner surfaces of the rails. Z scale is the smallest size. N scale is popular among modelers who do not have much space. The TT-scale is no longer commonly used. The greatest variety of engines, cars, and other supplies is available in this size, often referred to as HO gauge.