The ge_gameplayinfo entity is the mapper's primary resource for accessing gameplay related information, through its many different inputs and outputs. It also provides a means of modifying the floor height used by the radar.
In general this entity is very useful for fine-tuning your map based on distinct gameplay needs. Maps with campable dead-ends might want to use the OnSuperfluousAreasDisabled output to close these areas off to prevent players from camping there with the Golden Gun or a Flag. OnGameplayMatch can be used to trigger gameplay specific behavior, such as having a special golden gun room open up on Man with the Golden Gun. There are many possibilities, though in general you should avoid changing the location of important weapon spawns or critical passageways as this often just confuses players.