In this context, a "GUI" (Graphical User Interface) is a custom menu that appears on a player's screen to provide extra functionality beyond the standard game controls. These scripts are often created by the community to add features like:

The phrase typically refers to a specific script or interface used in the Roblox game City 8 , which is a popular roleplay map based on the Half-Life 2 universe.

Menus for changing jobs, managing inventory, or interacting with the environment.

Tools used by game moderators to manage players or server settings.

Custom HUDs (Heads-Up Displays) that match the gritty, industrial aesthetic of City 8.