Not a lot of detail to be honest:

World use to have several crystals that expanded civilization but misuse caused their power to fade away, only Noctis' country still has a working crystal and its currently in a cold war with the other nations that want their crystal.

Noctis' family runs the country and they are more like the mafia than a standard government/monarchy.

One nation finally attacks the capital to get the Crystal, its unknown how they fare but considering FF loves the "You can't thwart Stage one" trope I'm pretty sure they succeed and a large part of the plot will be trying to get it back.

Noctis has special powers possible due to his families connection to the crystal. He also can see the door to the land of the dead where Etro resides possibly because of a near life death experience in his childhood and he shares this trait with the girl Stella who seems to be a female counterpart to Noctis in terms of ability and possibly backstory.

Take all of this with a grain of salt cause most of these details are from throw away statement by the creators or from out of context scenes in the trailers so I can be completely off about all of this.