This is one of the camera's optional articulation joints. It is only used for left-handed users if they wish to orient the camera so that the arm is on the right-hand side. The camera can be taken off its default connector (friction fit, no tools required) and mounted using the Left-hand connector.
Please see below for instructions on how to do this:
Step 1. Detach the arm from the base.
Step 2. Firmly grasp the top of the arm in one hand and the camera in the other.
Step 3. Separate the camera from the arm by gently but firmly moving the camera side to side.
Step 4. Attach the camera back to the arm using the Left-hand connector.
Step 5. Attach the arm back to the base.
Note: Please be careful not to pull on the cable during the process as you may damage your OKIOCAM.