A functional React component is just what its name suggests—a function. Picture the render() method of any React component that you've seen. This method, in essence, is the component. The job of a functional React component is to return JSX, just like a class-based React component. The difference is that this is all a functional component can do. It has no state and no lifecycle methods.
Why would you want to use functional components? It's a matter of simplicity more than anything else. If your component renders some JSX and does nothing else, then why bother with a class when a function is simpler?
A pure function is a function without side effects. That is to say, called with a given set of arguments, the function always produces the same output. This is relevant for React components because, given a set of properties, it's easier to predict what the rendered content will be. Functions that always return the same value with a given argument...
