The Apartment is your home base. Return here between games to adjust your character class, your appearance, or your equipped artifacts. You'll also find Lenore, your sparring AI raven buddy, wandering around the apartment as your roommate, getting himself snacks and watching tv.
Use the Map Table to change which game mode you're playing in. If you are particularly short, you may find the map table difficult to use. Set a different height in Oculus after calibration to make the floor farther away, making you effectively taller and the map table easier to use.