A pendulum works by tapping into your intuition and sixth sense. The pendulum acts as a form of receiver and transmitter, from your higher guidance, guardian angels and spiritual teachers. As the pendulum moves, you gain answers in response to questions – it is best suited to use to answer ‘yes’ or ‘no’ questions. Some people describe the way a pendulum works as being like bringing together the rational and intuitive sides of you (the left and right sides of your brain). When these two elements are brought together, you’re able to make decisions using all the sources, rather than just one of them.
For a beginners guide to dowsing with a pendulum: https://lettertorobin.wordpress.com/