If you're in prison and married, you may occasionally get conjugal visits with your spouse. That means you and your spouse get to go into a trailer on the prison grounds and git yerself some lovin'. But you can't get conjugal visits with anyone unless you're legally wed, so better get that ceremony out of the way before you rob that convenience store.
Other than that, I got no idea about conjugal visits. I've never been to prison -- they pinned the nailgun murders on someone else, ha ha!