What is the main difference between tendonitis and carpal tunnel?

Big difference. Tendonitis refers to inflammation of a tendon or tendons, carpal tunnel is compression of the median nerve. Both can cause pain, and some of the treatments are similar (rest, immobilization, injections). Sometimes it is easy to distinguish between them sometimes not.
Numbness and tinglin. Numbness and tinhling for carpal tunml sybdrome tendonitis is painful tender tendon.