We just learned about the Driving Wheel.
Another part of a steam locomotive is the Leading Wheel.
These wheels are in the front of the train, and are used to help hold up the front part of the locomotive.
They are not the driving wheels that are moved around by the steam engine, they just roll along when the driving wheels push the train along, and help hold up the train.
(from: wikipedia - leading wheel)
Kid Facts - Blast from the past: Valve Spring