Join Date: Aug 2009
Location: New South Wales, Australia
As others said - you can just feel it when you're on board. A walk is one that is calm, slow and easy to sit to. You'll find that when you start trotting and you're not used to it you'll be thrown upwards a bit, then come back down. It will be bouncy and not at all like the walk. Then next one up is a canter, and rather than throwing you up and down, it's more like backwards and forwards. They all feel very different and once you're riding generally you can pick them very easily.
There are other "gaits" but they are generally restricted to gaited breeds, and aren't something you'll probably encounter until you ride a bit.