Category:Sorted by gauge
The "gauge" of a model train or locomotive refers to the width of the track that it runs on.
Categories such as "five inch gauge" are fairly self-explanatory - the track rail spacing is five inches.
There's also a more abstract numbering system for popular gauges where smaller numbers represent smaller sizes of track, giving gauge 2, gauge 1, the gauge 0 size that was popular at the beginning of the Twentieth Century (when they ran out of numbers), and then the tabletop "half zero" standard that's half the size of gauge 0, 00-gauge.
00-gauge was popularised in the UK by Hornby with their "Dublo" ("double-oh") brand. The US counterpart to 00-gauge is H0 ("haitch-oh", half-zero).
For technical reasons, model trains tend to have wheels that are out of scale to the rest of the model. "00" and "H0" models can use the same size of track, so technically, they could be argued to be the same gauge, but the two standards dictate different scalings for the size of the rest of the locomotive and carriage superstructure, so 00 and H0 models are not quite the same scale.