What you are seeing is a demonstration of how to work with the primary points in the male body for the energy to circulate better when doing a tantric form of massage. It is important that you only practice this on people who have good health as you are blocking some nerves and arteries that run into the extremities.
Keep in mind this is to help the recipient become more aware of bodily sensations and harmonize their yin and yang flow. Take your time when pressing on these points as they can be very sensitive. Only push down (slowly) as much as they feel comfortable.