This 12m long x 12mm wide roll of PTFE tape is WRAS approved for use with potable (drinking) water.
PTFE tape is used for sealing threaded plumbing connections.
PTFE stands for Polytetrafluoroethylene, though it's often called white tape, thread seal tape or plumber's tape,
The picture above shows how to use PTFE tape. You normally use 3 to 4 turns of tape, starting from the end and in the same direction as the threads.