Amestris is where everything takes place in the Fullmetal Alchemist series. Ishbal is just on of the many regions within Amestris, and Central City is the hub city for the whole country.
In this land Alchemy has become huge part of life. It become an every day tool, and weapon. Though It has also created some horrible things. Also Science has become less popular,so technology has slowed down. The only place that doesn't except Alchemy is Ishbal. A religious region in Amestris, that believes Alchemy implys that their creations are above Gods.
It also a counter part to Germany.