What is React.Component in detail?

https://www.codecademy.com/paths/web-development/tracks/front-end-applications-with-react/modules/react-101-react-components-u/lessons/your-first-react-component/exercises/component-class
I started to create react components, and I am interested in what React.Component is? Actually I learned that its JavaScript class , but what does it mean? Well, React is a JavaScript object , so where is the connection? Is Component class inside React object, so thats how we access this Component class typing React.Component and then subclass it in our code?