"Kingdom Hearts 3" will officially end the Xehanort trilogy, which encompasses the war between Sora and Xehanort. However, despite having three main games and multiple spin-offs, the titular land of Kingdom Hearts has never been explored or identified. According to The Gamers Joint, Kingdom Hearts may be a land of pure light.
According to the video, the developers have confirmed that Kingdom Hearts will be finally revealed in "Kingdom Hearts 3," indicating that it may be explored either via a cutscene or that it may be a fully realized world that players can traverse.
Kingdom Hearts has been hinted at throughout the games and the report points out that the few images of the open doors leading to Kingdom Hearts indicate that it may be a real, physical place that can be explored. If this is true then the place may be considered the exact opposite of the Realm of Darkness.
Back in the first "Kingdom Hearts" game, it was stated that Kingdom Hearts is light, leading many to speculate that the land of Kingdom Hearts is comprised of pure light. It is unknown if there is anything else within the land's environments, like trees and villages or towns filled with people.
Many of the spin-off titles have explored the mythos of Kingdom Hearts, and as stated in a report from Design and Trend, the series has already introduced abstract worlds in the past such as the Betwixt and Between worlds as well as the aforementioned Realm of Darkness.
The Keyblade Wars have also been teased in past titles as a war involving many warriors fighting for the power of Kingdom Hearts, indicating that these past warriors may have been able to draw power and to even explore Kingdom Hearts at will using the power of their Keyblade.
"Kingdom Hearts 3" will be released for the PS4, although Square-Enix has yet to announce an official release date.