What is React, and why is it used? What are the key features of React? What is JSX in React? Explain the concept of the Virtual DOM. What is the difference between functional and class components? What are props in React? What is state in React? What is the difference between state and props? What are React Hooks? How does useState work? What is useEffect used for? What is useMemo in React? Explain the purpose of useCallback. What is Context API in React? What is prop drilling, and how can you avoid it? What is lifting state up in React? What is the difference between controlled and uncontrolled components? What is React Router, and how does it work? What is the difference between useHistory, useLocation, and useParams in React Router?