Game passes allow Roblox developers to create special passes that can only be bought once per player using Robux. They can be used to give players special access to a restricted area, an in-game avatar item, or a permanent power-up.
While Roblox offers many tools for free, like Roblox Studio and hosting your games online, it does charge a Marketplace Fee for any purchases players make in your game. The money earned through this fee helps Roblox continue to provide new features and keep online servers for your games running.