I am impressed with both the definitions of MarkV and JMIII. John's is certainly short and to the point. As often as this subject gets asked and answered with more confusion added than clarification provided, they have given some solid information. Still likely hard for some to follow, as actual experience with the three 'controls' is usually the most helpful.
For draft, when you are plowing with a 3pt plow, and see the response the 3pt arms make 'automatically' when the plow draws deeper, and the ag wheel bars spin out a bit of dirt causing the plow to go even deeper, after which (or during which) the 3pt arms lift slightly to raise the plow, giving the wheels a chance to re-gain traction, then see the 3pt arms lower a bit to let the plow drop back down - then you begin to understand draft control. With no draft control, one only can use the 'position' control to do manually what the draft control does 'automatically'. Now I stop for fear of adding confusion.