The patch takes the game from version 1.16 to 1.17 and basically adds two new things:
1) the game now has the USA as a new country, it's ported from Democracy 1 and added to the end of the list.
2) The game now has mod support for people to add new voter types, such as drug users, atheists, ethnic minorities etc etc. It might be worth keeping aneye on the games modding forums to see what new mods get developed