Cock rings, penis rings, couples rings are all descriptive terms referring to rings worn by men that either enhance his sexual experience or when a vibrator is attached also enhance the woman's enjoyment as well. Whatever you call them the results are the objective is to gain harder, faster and more explosive orgasms by women and to help a man maintain his erection longer and harder. That in a nutshell describes a satisfying sex life and while cock rings can assist in that the objective is to strive to reach that result all or most of the time you engage in sexual relations.
Cock rings are used by many men and most report good results and if used correctly there should be good to very good results. Cock rings may be hard cold steel or soft, stretchy rubber but the results are the same. Due to the way the penis is created a strong, tight grip on the outer penis will result in blood not being able to exit and thus the man's erection will remain stiff and hard. It is not really any harder than that. The vibrating component is solely for the woman and the objective is to place the vibrator against her clitoris, vibrating against it intermitently or leaving it against her clit until she reaches an orgasm. What could be simpler?