A chiropractor is a specialist in adjusting the spine and correcting nerve flow. He's also a specialist in detecting things you wouldn't ordinarily expect him to find, based on some rather simple techniques involving his expertise in the flow of the nervous system.
Basically, this is what my chiropractor would do.
He'd have me hold out one arm or the other. Then he'd put a finger or two on various locations (particularly along the spine, but he wasn't limited to that) and then ask me to resist his attempt to push down my arm. Based on how easily he could push down my arm, he'd treat that as a reading that something was amiss. Then he could move to adjust whatever it was he'd detected, which could be having me lay down so he could apply an abrupt pressure to my spine to "crack" it (the vertebrae right near my gall bladder, for example, were off center), or on my back with my head in his hands to quickly turn my neck (that startled me!) to adjust it, or just stand there while he used a small device which applies a small bit of pressure in an area the size of, say, a pencil eraser. Rather noisy little thing.
Anyway, his goal was to get the pinched nerves unpinched, and the spinal column and related bones aligned properly. He did a fantastic job on helping me get through the shoulder pain I was experiencing.