I am going to answer this question, along with other frequently asked questions about hypnosis, as they are all related:
"Why Do Hypnotists Snap Their Fingers?"
"Why Do Hypnotists Use a Pendulum?"
"Why Do Hypnotists Tap Your Body?"
Let's start by saying that the subconscious mind is a brilliant part of your brain. Your subconscious mind is able to bring about feelings and emotions based on specific, external stimuli. For instance, think about the last time you ended a relationship. Did any songs, smells or places suddenly make you sad because you experienced those activities with your ex boyfriend or girlfriend? Chances are, they did. This is because your subconscious mind was able to connect a specific song, smell, activity or place with what was going on in your life. These are called anchors.
An anchor in hypnosis is a behavior that is associated with a particular state of mind or mood. There are different types of anchors, as referenced above, and are technically referred to as auditory, visual and kinesthetic anchors.
Hypnotists snap their fingers and make sounds with their mouths in order to create an auditory anchor. So when they are embedding a message into your subconscious, they will create these sounds in order to anchor a feeling with the message they are embedding. These auditory anchors also act as a cue for your mind to accept and act on the embedded suggestion.
Hypnotists use pendulums, watches and other objects in order to create a visual anchor in the same manner. Objects like pendulums and the watches hypnotists swing in front of a subject's eyes are also used to induce the person into hypnosis. A swinging object will a) tire someone'e eyes allowing them to enter a hypnotic state; b) increase a person's ability to focus on the hypnotist's words better; and, c) create a visual anchor between a specific object and emotion.
Hypnotists frequently tap people on their shoulders, knees, wrists, arm and limbs in order to create a kinesthetic anchor. Kinesthetic is a learning style in which learning takes place by a person carrying out physical activities. When a hypnotist taps someone's body, what they're doing is simply creating an anchor between the feeling of being touched and a specific embedded message.
In the YouTube video link above, you can see an example of how I used all of these hypnosis techniques simultaneously to induce hypnosis in a volunteer.