Welcome to the forum gekisen.
Thats spare sticky pad - spare mount ( probably there are 2 in different thickness ) and the thin EVA pad is to out on in between the camera and mount as after some time there can be a gap there and it can rattle.
The clear plastic is a static pad i think can be used if you do not want to stick to the glass itself, or just for a test fitting,,,,,, personally i have never used them.
The string is a band saw, you can use to saw thru the sticky tape to remove the camera some day, just be sure to keep parallel to glass as it can also saw into the plastics of the mount.