Dowsing is the exercise of a human faculty, which allows one to obtain information in a manner beyond the scope and power of the standard human physical senses of sight, sound, touch, etc. This is possible using tools, the body or using intuition or paranormal abilities / the human ~body  (=deviceless dowsing). Dowsing with a pendulum, rod or other instrument is a type of divination, what is perceiving/having knowledge of the hidden and comes from the subconsciousness of a person.