A pendulum is a weight (such as a stone, crystal) attached to a string or chain. Pendulums can be used as tools of divination to answer specific questions. When you ask a question, the pendulum will swing one way for "yes" and the other way for "no". Some pendulums swing clockwise and counter clockwise others will swing from side to side. It is always best before you ask your question to have the pendulum show you which way it swings for yes and no. A good example of this would be to say to your pendulum "show me yes" and see which way it moves. Then do the same for "show me no"
If you would like to know how to use a pendulum:
How to Use A Pendulum