This view means no masturbation or porn or cheating or pre-marital fooling around. But I think it is a little different now, and worse:You keep the keys to your sexuality until you are married, then you give them to your spouse. Only your spouse is allowed to use them.
This still disallows the activities above, but I think this distinction highlights the church's role. You are born with your sexuality, whatever it may be. It is yours and only yours. Then the church tries to convince you that in order to be a good, worthy child of god, you must do what they say with it. It's gotta fit in their box. Their box goes against natural human development in many cases. And their box prevents people from understanding their own sexuality at all. If you break their rules then they bury you with guilt. If you don't break their rules then you are in for a rough wedding night, and possibly rough marriage. If you break their rules and actually know how your sexuality works then your spouse may hold that against you. Since the church has given your spouse the keys to your sexuality what do you do when they are interested and you aren't, or vice versa?The church attempts to take the keys to your sexuality, then gives one to your spouse. Only your spouse is allowed to use it.
To be fair, the mormon church is not the first group to do this, nor are they the worst. But it's still messed up.