Almost every extension tube with electronics has them. What are they for?
They are so you can detach the lens. The lens latches in place on it and you push the button to allow it to be removed. This is the same function as the lens release on your camera.
When you go to put the tube on your camera you should attach the lens to the tube and then the assembly to the camera. When you are removing it, you reverse the process. Push the lens release on the camera, remove the entire assembly. Then push the button on the extension tube so that you can remove the lens.