"Until the advent of the advanced tractors of the middle twenties with all gears enclosed and air cleaners keeping dust and sand out of the cylinders, nearly all field and orchard work was done by horses. The two horse team was standard, but for cultivation of row crops, one horse was used. While nearly anyone from six or eight years up would drive horses after a fashion, provided the horses were not nervous or unruly, yet a few men had a skill with them that most could not approach. Horses had minds and personalities, no two alike, and there was much more difference in between the better horsemen and the poorer ones than between the poor and good drivers of cars today. I was somewhere in the middle in this. I knew men who were much better and some who were poorer".
"I have seen movies that included a man plowing. Invariably he would stagger around, hanging desperately to the handles, as though the plow was alive and trying to jump out of the furrow. Actually, plowing with a walking plow was one of the easiest jobs on the farm. On level ground, free of stones, a properly adjusted plow needed no guiding at all. With the reins around one's waist and hands on the plow handles, one expended less energy than simply walking along a road".
"A year or so ago the Atlantic Monthly printed an article by a man who had worked heavy draft horses in the west in his youth. He remarked that it was important never to let a team of horses run away, as they would then be 'spoiled'. However, we had four runaways in my experience, one with me, or from me, but none of the horses seemed different afterwards".
Answer to my question: A bridle is used to control a horse. It has a bit that fits in the horse's mouth to which the reins are attached. A halter in used to lead or tie a horse. It just goes around its nose and neck. Nothing in the mouth. Wikipedia has good pictures.