(as an aside, and if you're interested, a topic for later could be justice and fairness. I have found a huge difference between how I see them and how religious people see them.)
As a naturalist/atheist/skeptic/science lover, while I don't understand the physics, mechanics, biochemistry and biology of the workings of the brain, I understand that the mind is what is active in the brain. That's not the best wording, but basically the mind is just the brain, but I think of it as RAM whereas the physical structure of the brain is more like the Hard Drive. If you have a better analogy, please share it. They are one and the same, essentially. Your mind is not separate from your brain.
Imagination: the ability of forming mental images, sensations and concepts, in a moment when they are not perceived through sight, hearing or other senses. Imagination is the work of the mind that helps create. Imagination helps provide meaning to experience and understanding to knowledge; it is a fundamental facility through which people make sense of the world, and it also plays a key role in the learning process.
Creativity: 1. having the ability to create. 2. characterized by originality of thought; having or showing imagination. 3. designed to or tending to stimulate the imagination.
So we all use our imaginations every time we have a thought that creates something in our minds that is not perceived through our senses. Like pink elephants with emerald green polka dots. If you can see them standing on top of each other in your head right now, you are using your imagination.