Where is the center of the Earth?

Could you please elaborate on the concept of the center of the Earth? I'm curious to know, what exactly is located at the very core of our planet? Is it solid or hollow? What materials compose it? How does it affect the structure and functions of the Earth? Furthermore, have we been able to explore and study this mysterious center, and if so, what have we discovered? I'm fascinated by the idea of what lies beneath our feet, and I'm eager to learn more about it.