What make you confused @brother @starl? As I learnt at my college, vasectomy is one method of man contraception. But it will not cause erection dysfunction. So the man still can have sex normally, but the sperm cannot go out.. which prevent him from having a child. The incidence of impotence among man after vasectomy is rare.

https://www.healthline.com/health/erectile-dysfunction/impotence-after-vasectomy