Benedict Baker's depiction of the Procedural.
Realms are locations within the Entity's World. Each Realm was the site of a violent tragedy in the past and now serve as the arenas for the Entity's trials.
The location of the trial is chosen by The Entity. Players can influence The Entity's choice by burning certain Offerings.
Trial locations have certain fixed landmarks, but elements such as player starting locations, generators, chests, totems and exits are placed according to The Entity's whims. Even the terrain itself shifts from trial to trial.
There are currently 8 Realms and 20 Maps in Dead by Daylight.