Types of "shows"
On most cam sites, there are 3-4 basic types of show/chat sessions available. They are named differently on each site, but the basis is usually similar to the types listed below.
In Free or Public chat, you normally will be visible by anyone who comes to the site, whether they have an account or are just visiting as a guest. It is considered "free" in the sense that there is no pay-per-minute aspect to it, though you may be able to receive tips from members. Public chat is where you appeal to your potential paying members to either tip you, take you private, or join a group or other form of paid show. Some sites do not allow you to show any nudity in Public chat, so make sure to read the rules of each site to determine what you're allowed to do in Public.
Private with voyeurs
A Private chat is pay-per-minute (at whichever rate you, or the site, sets for it). On most sites, the member that initiates the private show with you will be the only one who can chat with you, but other "voyeurs" may watch the video portion of it, also paying a lesser pay-per-minute rate. On some sites, your private shows may be recorded by the site, and either offered to the person who paid for the private, or also offered for an additional fee to other members. Make sure to check with the site you're on about their policies and practices regarding privates being recorded.
On Streamate, a "Premium" show is actually more like a Group show. See below for info on Group shows.
Private with no voyeurs
A Private chat without the ability for others to watch or participate. Normally these are offered at a higher per-minute rate since there is no ability to receive extra income from voyeurs, but it varies by site.
On Streamate, the "Exclusive" chat is a non-voyeur private show.
A Group chat is a pay-per-minute show where multiple members are included and are all paying the same rate and have the same level of participation.
On Streamate, Premium chat is a type of group show. One member must initiate the Premium chat, but after that any member may enter or exit as they wish, with every member paying the standard rate that the model chooses for Premium shows. The show continues until the model ends it or the last member leaves Premium chat.
This show type is specific to Streamate. GOLD shows are a type of group chat, but the entire show is prepaid instead of members paying per minute until they decide to leave.
When a model starts a GOLD show countdown, she chooses the following limits: what will be done in a GOLD show, how many minutes the show will be for, the minimum amount each member must contribute to see the show, how much GOLD she wants before she will start the show, and how long she will wait to reach her goal before she starts or quits the show. Models may choose to begin the show at any time, even if the timer has not finished or if she has not reached her goal. If the model chooses to cancel the show without starting it, all members will be refunded their money and the model receives nothing.
When the model chooses to start the GOLD show, she and all the members who contributed the minimum amount are taken to a private group chat. Even after the show begins, members may still enter at any time and will be charged the full minimum amount. The members can see and talk to each other if they so choose.
GOLD shows are different than other types of group shows because it is prepaid and only lasts for a specific amount of time.