What is closed in tubing head pressure in Oil and Gas industry?

usually, the tubing head is the cross-tee connected by flange both at top and bottom. The tubing head is installed on the flange of the casing head, so as to hang the tubing string and seal the annular space between the tubing string and the production casing. The tubing head is made up of the tubing head cross-tee and the tubing hanger.