Training a Sheepdog

One day a week or two ago, I went into the living room and noticed our landlord on the hill above our house, on his motorbike (4-wheeler). He had one dog with him, and the dog went into the trees near the top of the hill and herded a small mob (maybe 50) of sheep out. He bunched them in a tight mob, then headed them across the hill below the trees. The dog took the sheep back and forth a couple of times, with no apparent purpose, but we found out later that he was just being trained. It was quite fascinating to watch!