A region is an internal grouping of nations in NationStates. You can choose what region you are in, with a few exceptions(see Banlist).
There are two types of regions: regions that were created by the game admin ("game-created" regions), and regions created by nationstates players themselves ("player-created" regions).
Game regions would be the five Pacific regions, plus the Rejected Realms and Lazarus. They are also called feeder/sink regions. Game regions do not have regional founders and power tends to be concentrated within the hands of the WA Delegate. One major characteristic of game regions is that they are the largest regions in the game. Whomever is delegate of one tends to become very important. Other game regions are called Warzones, and are commited almost solely to the invasion game.