"Sooo it's a root that sends up a new bind??"
Actually, it's more like a bine (stem) that grows under the ground. Roots don't have nodes to send up bines. Runners have nodes and can create both roots and bines. Because of this, they are super easy to propagate. Simply cut them off and place in moist soil. BOOM, new hops plant.
More info: http://en.wikipedia.org/wiki/Stolon