Asking this question is not only interesting from a philosophical standpoint but also for very practical reasons. Moreover, it is extremely useful to guide the creation process. A superficial approach could say that people create stories, movies, books, fictional places to escape reality and distract themselves from their boredom. This could be a valid point and especially in the modern world where we have solved so many challenges that Humanity had before that we gained so much freedom that we end up bored and need to find distraction that gives us the excitement we do not find in real life anymore (let's face it, the lack of sabertooth tigers chasing us is a real plague of modernity). However, this understanding would overlook the fact that Humanity always had a great interest in fiction and imaginary worlds. We always asked ourselves what was beyond our own reality, what it would mean to experience life and the Universe in a different way.
Why This Is Interesting for Creators to Understand
There is a very simple biological reason to that. In our brains, we have mirror neurons that are being activated when we are doing a particular thing but also when we see somebody else doing it. This of course plays a critical part in the learning process and empathy but it also explains our fascination for fictional worlds. Simply put, we are not only feeling emotions about the worlds we experience but we are literally feeling the same emotions (at least in part) as characters in our worlds. When a character is a king, we feel a little bit what it would mean to be a king. If a character is fighting to protect her family, we feel a bit like we are protecting our family.
This has remarkably interesting implications because now we can understand why successful worlds work so well. They are allowing the creator and audience to experience being somebody else and having a panel of experiences much more diverse than a traditional human life could without this mechanism. Our brains can literally experience life as thousands of different characters having different lives in real or fictional universes. This can give a richness to our Human experience much more complete than we could think. This also explains why fictional worlds can be so addictive and why some people prefer to spend their time in these fictional universes rather than facing the real world. In essence, you and your audience will want to interact with your world in three main areas: thoughts and judgments, emotions and feelings about the physical world.
Thoughts, Ideas and Judgments
Your characters will have different ideas about what is happening in the world. They can have brilliant ideas about how to solve particular solutions, discover more about their reality, be opiniated about things and also change their minds. They can make hypothesis or present ideas to which your world will respond. And these interactions between their mind and their environment can bring interesting conflict, evolution of relationships between characters but also influence the world in major ways. You can also make different characters hold different world views and having them be in conflict about it. Your characters can also be on a quest for knowledge and develop their smarts or wisdom at the same time as the audience.
Emotions and Matters of the Heart
What would it feel to discover that your father is in fact not dead but the evil overlord you have been fight for nearly two movies? How would you feel by discovering that you and your beloved share a love that is immortal beyond life and death? How would it feel to know that you and the evil master that killed your parents are inextricably linked and that neither of you can live while the other survives? What would it be like to save your family from harm and knowing you put your life at risk for love and a higher purpose? All of these experiences can give you or your audience emotions that can run very deep and make you develop your emotional maturity well beyond what would be available if we did not have access to fictional worlds.
Who has never dreamed of dropping from orbit to the surface of a planet in a heavy bomber? How would it physically feel, to assault an enemy planet leading a squadron and facing enemy defenses? Gauss cannons trying to destroy you, the thrill of the acceleration felt and the adrenaline from the fight. Or maybe a barefoot walk on the beach with a lover at dusk, where the coral sea is lit by a myriad of neon fishes? Or exploring ancient ruins in lush mountains on a distant moon, hiking through a misty fog with a group of rogue scientists? Or feeling the wind and the ground shaking of a capital ship taking off? All of these feelings are things that you as creator and your audience can experience by interacting with your world.
The Value for Our Lives
On top of the obvious entertainment we get from experiencing fictional worlds, we also get advantages that can benefit our life in the real world. As we are experiencing the same kinds of ideas as our characters, we get to enrich our ideas, we get a different perspective about life, we get to experience life in other people’s shoes and we also get a better emotional maturity. All of these aspects can greatly enrich our lives and help us learn more about ourselves and about the World. We get to see different ways of being, different cultures, different people with conflicting personalities. This is why the value of fictional worlds should not be underestimated. As an example, anybody can be taught, shown and told that racism and xenophobia are extremely harmful. But how much more understanding do you get if you experience it? How much better do people remember if they lived situations of racism and xenophobia?
Whether you are thinking about the realms of ideas, emotions or physical feelings, the crux of everything is that the same neurons will fire in you and your audience as they would in your characters if they were real. And this is a really powerful thought to keep in mind when we are creating fictional worlds because you realize that there is no difference between the real world and your fictional world in terms of emotions and ideas for the brain.
What will make the difference between a successful experience and a failure is erasing this distance in the mind of your audience between your world and reality. If we take the example of a movie, it is successful when all aspects are working harmoniously together. If the music, story, camera angles, colors, costumes, dialogues, actors, backgrounds all do their job well, then the audience is pulled into your world and stops making a difference in their mind with reality. This is what makes world creation so powerful, this ability to make people believe and experience being in your world as if it were real.