system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does imagination work and why are some people more creative than others?
gpt
Simple and correct answer: it's very complicated and is studied by scientists.

Now then, here's a simplified answer that's sort of right:

Roughly speaking, the brain works by connecting ideas to each other.

When one person says "cat", the part of your brain that thinks "cat" starts becoming active. Now, in your brain "cat" is also connected to the ideas of: mammal, pet, Dr. Seuss, and so on. And then each of those ideas is connected to other things as well, the idea of Dr. Seuss might be connected to hats for example.

So when someone says "See that cat? The one near that hat?" The part of your brain that thinks "cat" lights up. And the part of your brain that thinks "hat" lights up. And because both of those ideas are connected to Dr. Seuss, you also think of the book he wrote called "The Cat in the Hat", and mention that to the person talking to you.

So imagination is when you experience something, and instead of just thinking of that thing that you experienced you also start thinking about other things that are related.

One person is more creative than another when they know more ideas, that are connected to each other in interesting ways, and they know how to let those ideas connect to each other and turn into a new idea. 
Practically speaking they also have to have a decent sense of what a good idea is too.

One thing to learn from this is that a brick layer who read a lot and took the time to think a lot about what and why they were writing, would probably be just as creative as a person trained to be a poet. You don't even need to be intelligent to be creative. The reason brick layers don't often become stellar poets is simply because brick layers don't usually have the education, time, or luxury to develop the necessary skills.