What is the difference between posterior tibial tendon and tarsal tunnel?

Different things: A tendon is the end of a muscle that connects the muscle to bone. The posterior tibial tendon attaches the tibialis posterior muscle to certain bones of the foot. The tarsal tunnel is an area by your heel where the posterior tibial tendon along with 2 other tendons, a major artery, vein and nerve, pass. Its a tight area bordered by bone and thick soft tissue.

One is a tendon : While the tarsal tunnel is an area or region of the ankle where tendons, nerve and vascular structures pass into the foot. It is the equivalent to the carpal tunnel in the wrist. These structures can be compressed within the tarsal tunnel leading to various symptoms like pain, numbness and tingling.