Your spine protects your spinal cord and the nerves that come from the spinal cord. Your spinal cord and your nerves are how your brain and body communicate with each other. This communication is done by sending a sort of electrical signal over the spinal cord and nerves. Knowing this, you can then think of anything in your body that is connected to nerves (muscles, lungs, stomach, etc.) like “electrical appliances” of your body. If they're plugged in, they work. If they're not plugged in, they won't work.
To take this analogy further, think of a light. It’s an electrical appliance, and when it's connected to electricity, it works. When it's not connected, it doesn't work.
Now, what if I used a dimmer switch to cut down on the current going to the light bulb? The light would still work, just not as well or as brightly as it potentially could be shining.
Your spine is made up of 24 movable vertebrae which I like to call "switches". When these switches get stuck out of place (which chiropractors call subluxation), they interfere with communication between the brain in the body. If that interference is in an area of the spine with nerves that go to the stomach (for example), the stomach will still work, just not as well as it could be working. Now apply this idea to other parts of the body.
Chiropractic is not a cure all or really even a cure anything, because most health conditions have multiple factors that cause problems. Chiropractic very simply, yet powerfully, lays a solid foundation for the body to perform as well as it can.
No matter what symptoms a person has, or better yet, even if a person has no noticeable symptoms, a person is always better off with a good nerve supply than with a poor nerve supply.