React Hooks are functions that let you use state and other React features in functional components. They were introduced in React 16.8 to simplify the way developers manage state and side effects without needing to convert functional components into class components. The most commonly used hooks are useState and useEffect. useState allows you to add state variables to your functional components, while useEffect lets you perform side effects, such as data fetching or subscriptions, in response to changes in state or props. This makes it easier to write and maintain React applications.