I see this is your first contact with Final Fantasy.

Final Fantasy XV is actually one of the most realistic games of the franchise in this aspect.

Found a Japanese script. Here is all the important stuff shown:

Walking the world

• The first video shown is a portion of the Dascae region which will be on the demo
• Events and enemy position removed/changed for this video to show just the walking
• You can eat and gather information at gas stations
• If you can see something in the background you can go to it
• Depending on the shape of the ground Noct and friends walking animations will change
• If you keep running you can see your friends tire and try to catch their breath
• You can fish in streams, rivers, and the ocean!
• You can fight the wildlife. As they are always active, be careful as they will attack if you get close
• There are buildings in the forest with people living in them. You can enter some of these buildings
• There are also animals that aren't enemies like cats and dogs
• In order to make the mountains the developers actually climbed one. They might show a video of them doing this one day
• Demons like the Naga or the Goblins will come out of the caves at night
• It's dangerous at night and is safer to rest at a gas station or by other means
• The party members dialogue will change in accordance to the time
• A Chocobo was shown in the forest. Look forward to finding out more in the demo
• The enemy airship patrols will sometimes land and fight you
• Magitek Armor will make an appearance. (was not meant to have been said)
• The Dascae region is as a large as 10% of the game