Partial penectomy (cutting your penis, surgical-style).

Use 2x speed of you have little time to kill. Use 1.5x speed IF you actually want to understand/know what's going on.

Why is this "thing" performed in the first place?

Short answer; to treat cancer. Especially penile cancer. There are other ways to treat such diabolical sounding thing - but this is just the one of.. a couple many. At least for this case - other reasons are usually for your.. gender thing. Yeah.

Long answer - and I quote;

This operation removes part or all of the penis. It's the most common and best known way to treat penile cancer that has grown deeply inside the penis. The goal is to remove all of the cancer. To do this the surgeon needs to remove some of the normal looking penis as well. The surgeon will try to leave as much of the shaft as possible.

The operation is called a partial penectomy if only the end of the penis is removed (and some shaft remains).

If not enough of the shaft can be saved for the man to urinate standing up without dribbling (at least 2 to 3 cm), a total penectomy will be done. This means the entire penis is removed, including the roots that extend into the pelvis. The surgeon creates a new opening for urine to drain from the perineum, which is the area between the scrotum (sac for the testicles) and the anus. This is called a perineal urethrostomy. Urination can still be controlled because the sphincter muscle (the "on-off" valve) in the urethra is left behind, but the man will have to sit to urinate.

For very advanced tumors, sometimes the penis is removed along with the scrotum (and testicles). This operation is called emasculation. Since this operation removes the testicles, which are the body's main source of the male hormone testosterone, men who have this procedure must take testosterone supplements for the rest of their lives.

Any of these operations can affect a man's self-image, as well as his ability to have sex.

Source;

https://my.clevelandclinic.org/health/treatments/22806-penectomy

https://www.cancer.org/cancer/types/penile-cancer/treating/surgery.html#::text=Partial%20or%20total,Penile%20Cancer%20Survivor