A Premium Pass is a little slip of paper that gives the purchaser private off-camera time (a Premium Visitation) with whomever it has been bought from. The relay isn't public, but people who are high up (such as CEO's (AD Day 10, strip 28)) or have a lot of money to spend can arrange to view these 'off-camera' times. (Though Kane mentioned getting a premium pass tile (AD Day 10, strip 33)
A Premium Visitation means that time has been purchased that will not be viewed by regular viewers, but only investors and those who can afford the price. The reason is varied. Sometimes, it's for social events. It's a status symbol to be able to purchase time from an indentured player, especially a popular one to accompany one somewhere as an escort. Some players are quite happy with the time off from the game and they are usually compensated, more depending on what the buyer wants. They don't have to do what is requested of them other than appear and chat idly. Other times,... a part of the request is more base, such as what was sometimes purchased from gladiators in the coliseums of Rome. A thrill. A challenge on occasion. (AD Day 10, strip 29)
These tend to be very expensive, so few can afford them, and the dice whose time has been purchased is required to spend time with the purchaser, and while expected to be civil and to fill reasonable requests, are not required to fill any and all requests. A few unscrupulous individuals have found a way around this.
Proper protocol calls for Visitors to at least introduce themselves before trying anything. (AD Day 10, strip 31)