Typically, the penis is quite sensitive immediately following an ejaculatory orgasm. This coincides with the refractory period and some people find their penis too sensitive to touch during this time. Hence, POT is the continued stimulation of the genitals straight after ejaculation.
Often uncomfortable and sometimes painful, POT can be likened to tickling. For a person who is ticklish, the sensation of being tickled can be overwhelming. Their body may involuntarily jerk and buck to escape. Similarly, the heightened sensitivity of the penis after ejaculation can cause that person to involuntarily kick and move to try and escape the stimulation.
Because of this, restraints are commonly used during POT. Incorporating bondage ensures the person being "tortured" cannot stop their "torturer." This adds an element of power play, whereby it puts the "torturer" in a position of power and makes the person being "tortured" feel vulnerable as they lose control over their body.
The key to successful POT is clear, open communication and consent between all involved. As this type of play does involve discomfort and potential pain, the person being "tortured" should share a safe word or physical action that indicates the "torturer" should stop.
When POT is performed on a person with a penis, try focusing on the sensitive glans. The "torture" will be most effective if it occurs while the penis is still erect. Cock rings can help maintain the erection after ejaculation.
Some people may sustain POT until the refractory period is over and the discomfort abates and the person being "tortured" is ready to continue sexual activity.
Another use of POT may be as a punishment for premature ejaculation or even as part of a game. If your partner comes too quickly, or before you, POT can be used in conjunction with other physical punishment or verbal degradation or humiliation to heighten the experience.