Sun Francisco is a new map for GTA. This version includes Chapter 1: Car Theft Vacation and Chapter 2: To Serve and Protect.
There are many cool features like F-15 flying (!), but I'm not going to list them all, you have to discover them yourself. New in Chapter 2 is that you play as a police officer, fighting against Hell's Angels and other criminals.
In the game, the map replaces the location San Andreas. Installation:make a backup copy of the gtadataand drop the files into it, confirming the replacement.