Private server

Private servers (formerly and commonly known as VIP servers ) are private per-game servers that are individually owned. As of June 12, 2020, developers can choose to make their private servers free (players may only own one private server per game). Prior to leaderboards being removed, they could appear as clans in the Clans section while viewing game leaderboards.

Creating private servers
If a developer has enabled private servers on their place, then players can create private servers for their place. Players will spend the chosen amount of Robux and then can choose a name, users allowed and have access to a link to the private server, and if friends are allowed to join. Then, the server can be seen on the servers tab. If the server creator shuts down the server or the developer disables private servers, then the server becomes unplayable.

Developer usage
There are two properties in that can be used to detect a private server. These properties are PrivateServerId and PrivateServerOwnerId. More information.

Bugs

 * When attempting to join a friend that is in a private server you do not have access to, you will be kicked. This has caused confusion among many players attempting to join and not knowing why they can't get in their friend's game.
 * When you shut down the server, players may not be instantly kicked.

Other

 * Players who do not use a web browser for roblox cannot join private servers through invite links, and instead have to rely on the server owner specifically inviting them through the configuration settings.

Use of private servers
Private servers are purchased and used for a multitude of reasons. Such reasons may include; With private servers being free in some games, they don't need to be purchased.
 * Regular players may use private servers for farming an in-game currency or item without the hassle of dealing with other players, in a clean isolated environment. It is increasingly common for RPG games and prison games to have players purchase private servers for easy farming. They could also use private servers to use content that the game's developer makes exclusive to private servers. It is also used to transfer funds after the group's delay on payout.
 * YouTubers also frequently own private servers, to make recording easier and prevent players from streamsniping them. They may also open private servers to be a public invite link, so fans of the YouTuber can join and play with other fans.
 * Developers may own a private server in their own game to make testing new features of their game easier.
 * Exploiters may also use private servers to automatically farm in games, without the worry of non-friends reporting them for exploiting.
 * Private servers are also sometimes purchased simply for privacy reasons. Players may wish to play in a game with only their friends, and no randoms.