On-screen UI container objects hold GuiObjects that you want to display on a user's screen. All on-screen UI objects and code are stored and changed on the client.
The StarterGui service is a container object that holds GuiObjects, such as a ScreenGui and its children GuiObjects. This service initializes on-screen UI for new users joining an experience. You do not need to create a StarterGui object as it is always present in the Explorer window.
A Player's PlayerGui is a container for that specific player's on-screen UI objects. When a user first joins an experience, the PlayerGui automatically inserts into their Player object within the Players service. Then, when the user's avatar spawns for the first time, the StarterGui service clones all of its contents into the PlayerGui container.
Creating a ScreenGui
In the Explorer window, hover over StarterGui and click the ⊕ icon. A contextual menu displays.
Insert a ScreenGui.