The most common way a human body moves is with volition, or free will. The central nervous system, by way of the brain, spine, muscles and all the other organs, directs the body to move and do whatever it does. Many of the underlying causes are not themselves chosen. There is the genetic makeup and various physical conditions of the body. There are experiences, thoughts, conclusions and other conceptual aspects that cause the volition to act however it does. Still, it is that volition which moves the body and causes the actions of that body, whatever they are.
There is power. Power can mean many things to different people. It can range from the crying of a baby to extremely complex beliefs of abstracted principles. These things all have "power" over a person but in this essay, power is used exclusively to mean PHYSICAL POWER. It may be called violence, coercion, force initiation, compulsion, physical imposition...it doesn't matter what it's called because it IS something. It's physics---it is one person or physical object having superior control over a person such that the person's volition is insufficient to physically overcome it.
Authority is a conceptual matter. It is volitional. A body may give sway to superior physical power, but any authority in the matter is strictly a matter of volition. The power only has authority over the body if the person chooses for it to have authority. People will frequently say otherwise and refer to things like "the authority of rules" or even more commonly, "what the authorities directed me to do."
There are two ways of moving any person, volition or power. That is an exhaustive list. No human body moves or does anything except by way of one of those two options, individual volition or physical power.