A dowser on a French farm
What makes the rods or stick move? You do! But not in the same way as when you reach out to pick up a fork or knife. These movements are conscious - you decide what you want to do and tell your body to do it.
What makes the rods move are tiny movements of your muscles. You're not aware of making these movements - they're made by your unconscious mind.
When dowsing is working, our unconscious mind is tuned to things we don't know. They may be things we've known at one time but have forgotten, or things we've noticed without being aware of it, or things we have become aware of with a sixth sense (when we dowse for water or something someone else has lost).
If you want to know more about dowsing and are an advanced reader, try these sites:
Tom Graves' article in Undercurrents
Dowsing photo from Flickr, taken by Irene Kightley.