A koan is a multi-level structure device that is used in Buddhism to help a person expand their awareness. Koans can be long or short, verbal or non-verbal. At first glance a koan often appears to be a meaningless phrase. However when you focus intently on a koan for extended periods of time, the natural reality can be revealed to you.
Koans often juxtapose two or more incongruous concepts.
Normally we think that it takes two hand to clap. Your finite mind can think about this, analyze it and get frustrated. Unlike your finite mind, your infinite mind is not bound by the rules of time and space. It has ten thousand states of mind to view and examine experience through. With the use of your infinite mind you can understand the clapping of one hand and many other things that would seem incomprehensible to your finite mind.