what is a Hook in React ?

In React TypeScript, a hook is a special function that allows functional components to use state and other React features that were previously only available in class components. Hooks allow you to reuse stateful logic across multiple components without having to use higher-order components or render props. They also help to keep the logic of a component separate from its presentation, making your code more modular and easier to maintain. Some commonly used hooks in React TypeScript include:

•   useState: allows you to add state to functional components 
•   useEffect: allows you to add side effects (e.g., data fetching, event listeners) to your components 
•  useContext: allows you to access a context object created by a ContextProvider component 
•  useRef: allows you to create a mutable reference that persists across renders 
•  useReducer: an alternative to useState that allows you to manage more complex state in a functional way .

To use a hook in a functional component, you simply call it at the top level of your component, and then use the values it returns in your JSX. For example:

In the example above, we're using the useState hook to add state to our Counter component. The hook returns an array with two values: the current state value (count) and a function to update the state (setCount). We then use these values to display the current count and update it when the button is clicked.