Cbt stands for cock and ball torture. You see,
CBT is a type of sexual activity that involves applying pain or constriction to the male genitals. This may involve directly painful activities, such as genital piercings, wax play, genital spanking, squeezing, ball-busting, genital flogging, urethral play, tickle torture, erotic electrostimulation, kneeing, or kicking. The recipient may receive direct physical pleasure from masochism, emotional pleasure through erotic humiliation, or knowledge that the play is pleasing to a sadistic dominant. Many of these practices carry health risks, of course.
Many devices might be used in CBT, such as ball stretchers, ball crushers, parachutes (which is a small collars made of leather that is fastened around the scrotum and from which weights can be hung), humblers (a BDSM restraint device that is used to restrict the movement of a sub and consists of testicular cuff device that clamps around the base of the scrotum and is mounted in the centre of a bar that passes behind the thigh at the base of the buttock), testicular cuffs, and cock harnesses, to name a few.
To learn more about CBT, I'd recommend searching it up on Pornhub or any porn site of your liking.