Ha ha, we're just passing the idiot ball around tonight!
A normal horse's intermediate gait is a trot. A gaited horse doesn't trot, but instead has an intermediate easy-gait. A running-walk is one of those trot substitutes. A running-walk has the same foot fall as a normal walk, only sped up. In a running-walk, there is to suspension; there is always a foot on the ground at all times. That's what makes it so smooth. (Unless you're Baby Girl. I've ridden smoother trotting horses!)