Scale: Scale is actually a simple ratio that describes how our model trains compare to trains in the real world. A Z scale locomotive is 1:220 the size of a real locomotive. Compare this to an HO locomotive, which is 1:87 the size of a real locomotive. Scale also refers to all the items on our model railway layouts… houses, trees, cars, etc.
Gauge: Gauge represents the distance between the rails on a track. There are essentially two families of railroad gauges, standard and narrow. These gauge classes apply to real railroads (also called prototype, prototypical or 1:1) as well as model railroads. Standard gauge prototype railroads have a distance between their rails of 4 feet, 8.5 inches. Narrow gauge prototype railroads are defined as railroads with a distance between their rails of less than 4 feet, 8.5 inches.