You have carpal tunnel in each of your wrists. It is formed by the carpal bones and the ligament that connects them with each other to form your wrist. A nerve that runs from your brain to your fingers passes through the carpal tunnel along with tendons that connect muscles of your fingers and hands to the bones.
When you make the same type of motion with your hand or wrist repeatedly, the tendons being used to make that motion may become swollen due to being overworked. If they become too inflamed, they press on the nerve passing through the carpal tunnel, which can cause pain, numbness or weakness in the affected hand.
The easiest way to prevent carpal tunnel syndrome is to be aware of the types of movements you make with your hands and be careful about how you make them. Variations in movements help when possible. Braces to prevent your wrists from bending may be needed. In some cases, surgery is needed to relieve the pressure on the nerve.